Chapter 6 — Sanitary Drainage
Gazette pages 4854–4910 · Official gazette pages (PDF, 1 MB) — use for exact tables and figures.
Sections in this chapter
6.1 Purpose
The purpose of this Chapter is to set forth provisions for planning, design and installation of waste disposal systems in and out of buildings 6.2 Scope
6.2.1 This Chapter specifies the general requirements for environmental sanitation for different categories of buildings according to their occupancy classification.
6.2.2 This Chapter also covers the design, installation and maintenance of drainage systems together with all ancillary works such as manholes and inspection chambers used within the building and from the building to public sewers or to offsite waste disposal system (i.e. into septic tanks and seepage pits or subsurface drainage system).
6.2.3 The disposal of wastes from industries, nuclear plants, slaughter houses, etc. are not covered by this Code. These wastes shall be properly treated as specified by environmental quality standards of Bangladesh before their disposal into public sewers or into natural bodies of water.
6.3 Terminology
This Section provides an alphabetical list of all terms used and applicable to this Chapter
of the Code. In case of any conflict or contradiction between a definition given in this
Section and that in any other Chapter or Part of the Code, the meaning specified in this
Chapter shall govern for interpretation of the provisions of this Chapter.
BEDDING The ratio of the product of design load and factor of safety to the
FACTOR minimum crushing strength.
BRANCH Any part of the piping system other than a main, riser, or stack.
BRANCH The length of soil or waste stack corresponding in general to a
INTERVAL storey height, but in no case less than 2.5 m within which the
horizontal branches from one floor or storey of building are
connected to the stack.
BRANCH VENT The vent connecting one or more individual vents with a vent
stack or stack vent.
BUILDING The building (house) drain is that part of the lowest piping or
DRAIN open channel of a drainage system which receives the discharges
from soil, waste, and other drainage systems inside the walls of
the building and conveys the same to the building (house) sewer,
beginning at 0.9 m outside the building wall.
BUILDING The building (house) sewer is that part of the horizontal piping of SEWER a drainage system which extends from the end of the building drain and which receives the discharge of the building drain and conveys it to a public sewer, private sewer, individual sewage disposal system, or other point of disposal. Also known as SEWER.
CIRCUIT VENT Venting of branch drainage pipe with which multiple fixtures are connected in battery.
DRAIN A drain is any pipe or open channel which carries waste water or waterborne wastes in a building drainage system.
DRAINAGE A drainage system (drainage piping) includes all the piping within
SYSTEM public or private premises, which conveys sewage, rain water, or
other liquid wastes to a legal point of disposal, but does not
include the mains of a public sewer system or a private or public
sewage treatment or disposal plant.
DRINKING A fountain or a tap with potable water supply connection. FOUNTAIN EXISTING The existing work is a plumbing system or any part thereof which WORK was installed prior to the date of enforcement of this Code.
FIXTURE UNIT A fixture unit is a quantity in terms of which the load producing effects on the plumbing system of different kinds of plumbing fixtures are expressed on some arbitrarily chosen scale.
FLUSH A flush valve is a device installed on the fixtures for the purpose VALVES of flushing those fixtures.
FRENCH A shallow trench filled with coarse rubble, clinker or similar DRAIN material with or without field drain pipes.
GRADE The grade is the slope or fall of a pipe in reference to a horizontal plane. In drainage it is usually expressed as the fall in mm per m length of pipe. HORIZONTAL A horizontal branch is a drain pipe extending laterally from a soil BRANCH or waste stack or building drain, with or without vertical sections or branches, which receives the discharge from one or more fixture drains and conducts it to the soil or waste stack or to the building drain.
HORIZONTAL A horizontal pipe is any pipe or fitting which is installed in a
PIPE horizontal position or which makes an angle of less than 45o with
the horizontal.
IMHOFF TANK These are two-storeyed settling cum digestion tanks used for primary treatment of domestic sewage in a very anaerobic environment.
INDIVIDUAL An individual vent is a pipe installed to vent a fixture trap and
VENT which connects with the vent system above the fixture served or
terminates in the open air.
INTERCEPTOR An interceptor is a device designed and installed so as to separate and retain deleterious, hazardous, or undesirable matter from normal wastes and permit normal or liquid wastes to discharge into the disposal terminal by gravity.
INVERT The lowest point of the internal surface of a pipe or channel at any cross-section.
KITCHEN SINK Sink or washing facilities raised above or at the level of the floor fitted with a tap.
LEADER A vertical drainage pipe that carries rainwater from roof or gutter drain to building storm drain or building drain or private disposal system. Also called Rainwater Down Pipe (RDP)
LIQUID WASTE The liquid waste is the discharge from any fixture, appliance, or appurtenance in connection with a plumbing system which does not receive faecal matter.
LOAD FACTOR The load factor is the percentage of the total connected fixture unit flow rate which is likely to occur at any point in the drainage system. It varies with the type of occupancy, the total flow unit above the point being considered, and with probability factor of simultaneous use.
LOCAL VENT A vertical piping to which connections are made from discharge
STACK side of traps and through which vapour or foul gas is removed
from the fixture or device used on bedpan washer.
LOOP VENT Also called Circuit vent. See CIRCUIT VENT.
MAIN The main of any system of continuous piping is the principal
artery of the system, to which branches may be connected.
MAIN SEWER See Public Sewer.
MAIN VENT The main vent is the principal artery of the venting system, to which vent branches are connected.
MANHOLE An opening through which a man may enter or leave a drain, a sewer or other closed structure for inspection, cleaning and other maintenance operations, fitted with a cover.
MANHOLE A chamber constructed on a drain or sewer so as to provide access CHAMBER thereto for inspection, testing or the clearance of obstruction. NON SERVICE A latrine other than service latrine. LATRINE
OFFSET An offset in a line of piping is a combination of elbows or bends which brings one section of the pipe out of line but into a line parallel with the other section.
PIPE SYSTEM The system to be adopted will depend on the type and planning of the building in which it is to be installed and will be one of the following :
(a) Single Stack System (Sec 6.9.3): One pipe system without trap ventilation pipe work.
(b) One Pipe System (Sec 6.9.3): The plumbing system in which the waste from sinks, bath rooms and wash basins, and soil pipe branches are all collected into one main pipe connected directly to the drainage system. Gully traps and waste pipes are completely dispensed with but all the traps of water closets, basins, etc. are completely ventilated to preserve the water seal.
(c) Two Pipe System (Sec 6.9.3): A discharge pipe system comprising two independent discharge pipes, one conveying soil directly to the drain, and other conveying waste water to the drain through a trapped gully. The system may also require ventilating pipes.
PLUMBING The plumbing includes the practice, materials, and fixtures used in the installation, maintenance, extension, and alteration of all piping, fixtures, appliances, and appurtenances in connection with any of the following: sanitary drainage or storm drainage
facilities, the venting system and the public or private water supply systems, within or adjacent to any building, structure, or conveyance; also the practice and materials used in the installation, maintenance, extension, or alteration of the storm water, liquid waste, or sewerage, and water supply systems of any premises to their connection within any point of public disposal or other acceptable terminal. PLUMBING The plumbing fixtures are installed receptacles, devices, or FIXTURES appliances which are supplied with water or which receive or discharge liquids or liquid borne wastes, with or without discharge into the drainage system with which they may be directly or indirectly connected. PLUMBING The plumbing system includes the water supply and distribution SYSTEM pipes, plumbing fixtures and traps, soil, waste and vent pipes, building drains and building sewers, including their respective connections, devices, and appurtenances within the property lines of the premises, and water treating or water using equipment. PUBLIC SEWER A common sewer directly controlled by public authority. Also known as MAIN SEWER. RELIEF VENT A relief vent is a vent the primary function of which is to provide circulation of air between drainage and vent systems (Sec 6.9.6). RISER A water supply pipe that extends vertically one full storey or more to convey water to branches or fixtures. SANITARY A sanitary sewer is a pipe which carries sewage and excludes SEWER storm, surface, and ground water. Also known as SEWER. SEEPAGE PIT See SOAK PIT. SEPTIC TANK A septic tank is a watertight settling tank which receives the discharge of a drainage system or part thereof and is designed and constructed so as to separate solids from the liquid, digest organic matter through a period of detention, and allow the liquids to discharge into the soil outside the tank through a system of open joint or perforated piping or disposal pit (Sec 6.9.13). SERVICE A latrine from which the excreta are removed by manual agency LATRINE and not by water carriage. SEWAGE The sewage is any liquid waste containing animal or vegetable matter in suspension or solution and may include liquids containing chemicals in solution.
SEWER See BUILDING SEWER or PUBLIC SEWER or SANITARY SEWER or STORM SEWER.
SLUDGE A settled portion of the sewage or waste water effluent from a sedimentation tank in semi-solid condition.
SOAK PIT A pit, dug into permeable soil lined to form a covered perforated chamber or filled with sand at the bottom and gravel or broken bricks at the top into which effluent from septic tank or storm water is led and from which these may soak away into the ground. Also known as SEEPAGE PIT or SOAK WELL.
SOAK WELL See SOAK PIT.
SOIL PIPE A soil pipe is any pipe which conveys the discharge of water
closets, urinals, or fixtures having similar functions, with or
without the discharge from other fixtures, to the building drain or
building sewer.
SOIL VENT See Stack Vent.
STACK A stack is the vertical main of a system of soil, waste, or vent piping.
STACK VENT A stack vent (sometimes called a waste vent or soil vent) is the extension of soil or waste stack above the highest horizontal drain connected to the stack. Also known as SOIL VENT.
STACK Stack venting is a method of venting a fixture or fixtures through VENTING the soil or waste stack.
STERILIZER A separate pipe or stack, indirectly connected to the building VENT drainage system at the lower terminal, which receives the vapour from non-pressure sterilizers or the exhaust from pressure sterilizers and conduct the vapour directly to the outer air.
SUBSOIL A subsoil drain is a drain which receives only subsurface or DRAIN seepage water and conveys it to a place of disposal.
SULLAGE The discharge from wash basins, sinks and similar appliances, which does not contain human or animal excreta.
SUMP A sump is a tank or pit which receives sewage or liquid waste, located below the normal grade of the gravity system, and which must be emptied by mechanical means.
SUPPORTS The supports, hangers, and anchors are devices for supporting and securing pipe and fixtures to walls, ceilings, floors, or structural members.
TRAP A trap is a fitting or device so designed and constructed as to provide, when properly vented, a liquid seal which will prevent the back passage of air or gas without materially affecting the flow of sewage or waste water through it.
TRAP SEAL The trap seal is the maximum vertical depth of liquid that a trap will retain, measured between the crown weir and the top of the dip of the trap.
VENT PIPE See Vent System.
VENT STACK A vent stack is a vertical vent pipe installed primarily for the purpose of providing circulation of air to and from any part of the drainage system.
VENT SYSTEM A vent system is a pipe or pipes installed to provide a flow of air to or from a drainage system or to provide a circulation of air within such system to protect trap seals from siphonage and back pressure. Also known as VENT PIPE.
VERTICAL PIPE A vertical pipe is any pipe or fitting which is installed in a vertical position or which makes an angle of not more than 45o with the vertical.
WASTE PIPE A waste pipe is a pipe which conveys only liquid waste free of faecal matter.
YOKE VENT A yoke vent is a vent provided between drainage and vent stacks to provide circulation of air between drainage and vent systems (Sec 6.9.6).
6.4 Drainage and Sanitation Plans
6.4.1 Requirement of Permit
Drainage and sanitation system shall not be installed until a permit for such work has been issued by the Authority for existing (only for addition or for alteration) or new building or for any other premises.
6.4.2 Application for Permit
An application for a permit for drainage and sanitation work shall be made on a prescribed form (see Appendix Q) by the licensed plumber and the owner, or by his appointed person or agent to install all or a self-contained or workable part of such work. The application shall accompany building drainage plans and adequate description of the proposed drainage and sanitation installation in a drawing (drawn to a scale not less than 1:100) with the following details:
(a) Plan(s) of the building with typical arrangement of plumbing fixtures
(b) Sanitary waste disposal system
(c) Venting system in the building drainage system
(d) Materials, sizes and gradients of all proposed piping
(e) Position of manhole, traps, waste pipe, rainwater pipe, vent pipe, water closet, urinal, lavatory, sink or other appliances in the premises and their connection with sewerage/drainage system or with private waste disposal system; the following colours may be used to indicate sewers, waste water pipes, rainwater pipes and existing works:
Proposed sanitary sewers and sanitary waste disposal pipes : Red
Proposed sanitary sewers and sanitary waste disposal pipes : Blue
Existing network : Black
(f) Position of refuse chute, inlet hopper and collection chamber for high rise buildings.
6.4.3 In addition to drainage plan a separate site plan of the building shall be submitted with the following particulars:
(a) Adjoining plots and streets with their identification
(b) Position and invert level of the public sewers (if any) and the direction of flow in it
(c) Level of the proposed drains connecting to the sewers (if any)
(d) Position and layout of private waste disposal system (in absence of public sewers); and
(e) Alignment, size and gradients of all drains.
6.4.4 For high rise buildings, design calculations and specifications for various items of the work involved shall be submitted along with the drawings.
6.4.5 Permits and Approvals
The building official shall examine or cause to be examined all applications for permits and, amendments thereto within 45 days. If the application does not conform to the requirements of all pertinent laws, such application shall be rejected in writing, stating the reasons therefore. If the proposed work satisfies all the Code requirements, the Authority shall issue a nontransferable permit.
6.5 Licensing of Plumber
6.5.1 License Requirement
No individual, partnership, corporation or firm shall engage in the business of installation, repair, alteration or maintenance of plumbing, drainage and sanitation work without obtaining a license from the Authority.
6.5.2 Examination and Certification
The Authority shall establish a plumber’s examination board. The board will determine the requirements for the qualification and procedures for examination of applicants for license. The Authority will issue license to such applicants who meet the qualifications therefore and successfully pass the examination conducted by the board.
6.5.3 Annulment of License
The license of a licensed plumber may be nullified by the Authority, if it is proved that a plumbing work has been completed and certified by the licensed plumber violating the provisions of this Code deliberately setting aside the approvals given in the permit or without receiving the permit from the Authority.
6.6 Drainage and Sanitation Requirement
6.6.1 General
(a) Each family dwelling unit on premises abutting a public sewer or with a private waste disposal system shall have at least one water closet and one kitchen sink or washing facilities. It is recommended to have at least one bathroom with a bath tub or shower to meet the basic requirements of sanitation and personal hygiene and in that case bath and water closet shall be separately accommodated.
(b) All other structures for human occupancy or use on premises abutting a sewer or with a private waste disposal system shall have adequate sanitary facilities but in no case less than one water closet and one other fixture for cleaning purposes.
(c) There shall be one water tap and arrangement for drainage in the vicinity of each water closet in all buildings.
(d) There shall be at least one water tap and arrangement for drainage in the vicinity of each urinal or group of urinals in all buildings.
(e) There shall be separate facilities for each sex for public toilets and for public bathing places based on the percentage of each anticipated sex.
(f) Where drinking water fountain is provided, it shall not be installed in toilet room.
(g) Rooms containing water closets or urinals shall be separated by partition wall from places where food will be prepared and served.
(h) All water closets and urinals shall be provided with flushing system.
6.6.2 Minimum Number of Fixtures
Table 8.6.1, Sections 6.6.2.1 and 6.6.2.2 provide the minimum number of fixtures required for different categories of buildings according to their occupancy classifications. The fixture requirement for the occupancy not provided in these sections shall be subject to the approval of the Authority.
6.6.2.1 The size of drainage pipe of fixtures shall be provided as shown in Table 8.6.2.
6.6.2.2 Automatic clothes washers
Waste connection: The waste from an automatic clothes washer shall discharge through an air break into a standpipe in. The trap and fixture drain for an automatic clothes washer stand pipe shall be a minimum of 2 inches (50 mm) in diameter.
6.6.2.3 Floor drains
Floor drains shall have removable strainers. The floor drain shall be constructed so that the drain is capable of being cleaned. Access shall be provided to the drain.
6.6.2.4 Physically handicapped plumbing facilities
All buildings other than residential, educational, storage and hazardous according to building occupancy classification, having public toilet facilities with required number of fixtures shall have at least one water closet for each sex (or one unisex water closet facility) and one drinking fountain accessible to and usable by physically handicapped persons. The water closet compartment for physically handicapped persons shall be in accordance with Sec 6.9.4.
6.6.2.5 Drainage and sanitation requirements for traffic terminal stations
(a) The minimum sanitary conveniences provided at any traffic terminal station like railway station, bus station etc. shall consist of non-service type latrines one for each sex, and one non-service type urinal for males for a daily passenger volume up to 300 persons. For large stations and airports, sanitary arrangements shall be in accordance with Table 8.6.1.
(b) There shall be adequate arrangements for satisfactory drainage of all sewage, sullage and waste water. The drainage shall be so designed as to cause no stagnation at the maximum discharge rate for which the different units are designed.
(c) Adequate scavenging arrangements shall be provided to keep the stations or terminals clear of all refuse. Refuse containers shall be placed at convenient points.
6.6.3 Accessibility
The fixtures specified in Sec 6.6.2 for public building shall be located not more than one floor above nor more than one floor below the floor occupied by the people for whose use the fixtures are intended, unless elevator service is available, except that in buildings which are accessible to the physically handicapped, there shall be minimum facilities as specified by the Code. It is desirable that the path of travel to the facilities shall not exceed a travel distance of 150 m.
Table 8.6.1: Plumbing Fixtures Requirement
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other
Occupancy or Shower (For male) Fountains Fixtures
A Residential A1 Single Family 1 per dwelling or 1 per dwelling 1 per - - 1 kitchen sink Dwelling apartment or apartment dwelling or per A3 Flats or apartment dwelling/apar Apartments tment
A2 Two Families 2 per dwelling 2 per dwelling 2 per - - 2 kitchen sink Dwelling dwelling per dwelling
A4 Mess, Boarding Houses and Hostels
For residence and MALE 1 kitchen sink
residential staff in each
1 per 8 1 per 8 1 per 8 1 per 25-150 kitchen
Add 1 per 1 per 75
FEMALE additional 50
1 per 6 1 per 6 1 per 6
For nonresidential MALE
staff
1 per 1-15 1 per 1-15
2 per 16-35 2 per 16-35
3 per 36-65 3 per 36-65 0 up to 6
4 per 66-100 4 per 66-100 1 per 7-20
FEMALE 2 per 21-45
- 1 per 100 -
3 per 46-70
1 per 1-12 1 per 1-12
4 per 71-100
2 per 13-25 2 per 13-25
3 per 26-40 3 per 26-40
4 per 41-57 4 per 41-57
5 per 58-77 5 per 58-77
6 per 78-100 6 per 78-100
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
Rooms wherein MALE
outsiders are
received 1 per 100 - 400 1 per water
Add 1 per closet and 1 per
additional 250 urinal or group
of urinals - 1 per 50 - -
FEMALE
2 per 100- 200 1 per water Add 1 per closet additional 100.
A5 Hotels and Lodging Houses
For residential 1 per 8 omitting 1 per 10 1 per 10 1 kitchen sink
public and staff the occupant of omitting the omitting in each
the room with wash basins the kitchen
attached water installed in the occupants
- 1 per 100
closet; Minimum room or suite. of the
of 2 if both sex room with
are lodged. bath in
suite.
For public MALE
rooms
1 per 100-400. 1 per water
Add 1 per closet and 1
additional 250 per urinal or
or part thereof. group or
urinals - 1 per 50 1 pe r 100 -
FEMALE
2 per 100-200. 1 per water Add 1 per closet additional 100 or part thereof.
For MALE
nonresidential
staff 1 per 1-15 1 per 1-15
2 per 16-35 2 per 16-35
3 per 36-65 3 per 36-65 0 up to 6
4 per 66-100 4 per 66-100 1 per 7-20
FEMALE 2 per 21-45
- 1 per 100 -
3 per 46-70
1 per 1-12 1 per 1-12
4 per 71-100
2 per 13-25 2 per 13-25
3 per 26-40 3 per 26-40
4 per 41-57 4 per 41-57
5 per 58-77 5 per 58-77
6 per 78-100 6 per 78-100
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
B Educational Facilities
B1 Education BOYS
Facilities up to
Higher 1 per 40 1 per 60 but
Secondary minimum 2 - Service sink:
Levels 1 per 20 1 per 50
GIRLS 1 per floor.
1 per 25 1 per 40 but
minimum 2
B2 Facilities for MALE
Training and
Above Higher 1 per 30 1 per 40 but
Secondary minimum 2 - Service sink:
Levels 1 per 20 1 per 50
FEMALE 1 per floor.
1 per 20 1 per 30 but
minimum 2
B3 Preschool 1 per 15 1 per 15 1 per 50 Service sink:
Facilities children children - -
children 1 per floor
C Institution for Care
C1 Institution for BOYS Urinals may
Care of be provided
1 per 8 1 per 8 1 per 8 in boys toilet
Children
rooms in lieu
GIRLS of water
closets but Service sink:
1 per 50
for not more 1 per floor
than ½ of
1 per 6 1 per 6 1 per 8 the required
number of
water
closets
C2 Custodial 1 unisex facility 1 per 200 1 per10 1 per 100 Service sink:
Institutions per or 1 for each Minimum 1 per floor
Physically sex per 1-100 1 for use -
Capable Adults by both
sexes.
C3 Custodial 2 unisex 1 per 200 1 per10 1 per 100 Service sink:
Institution per facilities Minimum 1 per floor
the Incapable or 1 unisex 1 for use
Adults facility and 1 for by both
each sex per sexes.
100-200. -
Over 200 one
additional
unisex facility
or 1 for each
sex for each
additional 100 .
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
C4 Penal and
Mental 1 per 15 1 per 100
1 per cell 1 per cell - Service sink
Institutions for children children
Children
C5 Penal and Mental 1 per cell 1 per cell 1 per 15 - 1 per 100 Service sink Institutions for Adults
D Health Care Facilities
D1 Normal Medical MALE -
Facilities Service sink:
1 per 8 patient 2 up to 30 1 per 8
(Indoor Patient patients and patients 1 per each
Ward) add 1 fixture ward.
per additional Bed pan
30 patients 1 per 75 washing sink:
FEMALE patients 1for each
ward.
1 per 8 patient 2 up to 30 1 per 8
Kitchen sink:
patients and patients
add 1 fixture 1 per each
per additional kitchen
30 patients
D1 Normal Medical MALE
Facilities
1 per 100 1 per 100
(Outdoor Service sink:
Patient Ward) FEMALE - 1 per 50 1 per 500 1 per each
D2 Emergency 2 per 100 1 per 100 ward
Medical
Facilities
E Business
E1 Offices MALE 0 up to 6 Service sink:
E2 Research and 1 per 7-20 1 per floor.
Testing 1 per 25 1 per 25 2 per 21-45
Laboratories 3 per 46-70
-
E3 Essential 4 per 71-100 1 per 100
Services FEMALE
Add@ 3% for
1 per 15 1 per 25 101-200 and
@ 2.5% for
over 200
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
F Mercantile
F1 Small Shops Urinals may Service
and Markets be provided sink:1
F2 Large Shops in toilet room
and Markets in lieu of
water closets
per men but 1 per
1 per 500 1 per 750 -
per not more 1000
than ½ of the
required
number of
water
closets.
F3 Refuelling 0 up to 6
MALE
Station 1 per 7-20 Service sink:
2 per 21-45 3 1 per floor.
1 per 25 1 per 25 per 46-70
- 4 per 71-100 1 per 100
FEMALE Add@ 3% for
101-200 and
@ 2.5% for
1 per 15 1 per 25
over 200
G Industrial Buildings
G1 Low hazard MALE 0 up to 6
industries 1 per 7-20 2 Service sink:
1 per 1-15 1 per 25
G2 Moderate per 21-45 1 per floor
hazard 2 per 16-35
3 per 46-70
industries 3 per 36-65
4 per 71-100
4 per 66-100
As required Add @ 3%
FEMALE by particular for 101-200
1 per 100
trades or and @ 2.5%
1 per 1-12 1 per 25 occupations for over 200
2 per 13-25
3 per 26-40
4 per 41-57
5 per 58-77
6 per 78-100
H Storage Buildings
H1 Low fire risk 1 per 100 1 per 100 Provisions - 1 per Service
storage per 1000 sink:1
H2 Moderate fire emergency
risk storage shower
I Assembly I1 Large assembly with fixed seats I2 Small assembly with fixed seats I3 Large assembly without fixed seats I4 Small assembly without fixed seats
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
Mosque 1 per 30 - 1 per 100 - 1 per 100 Water taps with drainage arrangement: 1 per 10
Junction MALE Stations, Min 2, 4 per Intermediate Min 2, 4 per 1000 Add Stations, 1000 Add 1 per Min 2, 4 1 per additional additional 1000. per 1000 Terminal 1000 Service sink: Stations and - Add 1 per 1 per 300 FEMALE additional 1 per floor Bus Terminals 1000 Min 2, 6 per Min 2, 5 per 1000 Add 1 1000 Add 1 per per additional additional 1000 1000
Domestic MALE
Airport 1Minimum Service sink:
2 Minimum 2 Minimum
4 per 200 4 per 200 2 per 200 1 per floor
6 per 400 6 per 400 4 per 400
8 per 600 8 per 600 5 per 600
9 per 800 9 per 800 6 per 800
10 per 1000 10 per 1000 7 per 1000
-
FEMALE 1 per 300
2 Minimum 2 Minimum 5 per 200 4 per 200 8 per 400 6 per 400 10 per 600 8 per 600 13 per 800 9 per 800 13 per 1000 10 per 1000
International MALE 4 shower 8 per 200
Airport stalls in 22 per 600 Service sink:
6 per 200 10 per 200 the
12 per 600 20 per 600 female or 22 per 1000 1 per floor
18 per 1000 25 per 1000 male toilet
in the
FEMALE transit
and 1 per 300
10 per 200 10 per 200
departure
20 per 600 20 per 600 lounge
29 per 1000 25 per 1000 and also
in the
main
concourse
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
Cinemas, MALE 1 per 25 Service sink
Concert halls, 1
1 per 100- 400 1 per 200
Theatres (for Add 1 per
public use) additional 250
1 per 500
FEMALE -
3 per 100- 200 1 per 200 Add 2 per additional 100
Cinemas, MALE 0 up to 6 1 per 500
Concert halls, 1 per 7-20 -
1 per 1-15 1 per 1-15
Theatres (for 2 per 21-45
2 per 16-35 2 per 16-35
permanent
employee use) FEMALE -
1 per 1-12 1 per 1-12 2 per 13-25 2 per 13-25
Art Galleries, MALE 1 per 50 1 per 500 Service sink: 1
Libraries,
1 per 200 - 400 1 per 200
Museums (for Add 1 per Over 200 add
public use) additional 250 1 per additional
250 -
FEMALE
1 per 100 - 200 1 per 200 Add 1 per Add 1 per additional 150 additional 150
Art Galleries, MALE 0 up to 5 1 per 100
Libraries, 1 per 7-20 -
1 per 1-15 1 per 1-15
Museums (for 2 per 21-45
2 per 16-35 2 per 16-35
permanent
-
employee use) FEMALE
1 per 1-12 1 per 1-12 2 per 14-25 2 per 14-25
I5 Sports Facilities MALE
1 per 75 1 per 60
1 per 50 1 per 75 1 per 300 Service sink:
FEMALE 1
1 per 50 1 per 60
Type of Building Water Closets* Wash Basins *** Bathtubs Urinals** Drinking Other Occupancy or Shower (For male) Fountains Fixtures
J Hazardous Buildings
J1 Explosion hazard building 1 per 100 1 per 100 Provisions - Service J2 Chemical hazard per sink:1 building emergency 1 per J3 Biological hazard shower 1000 building J4 Radiation hazard building
K Garage
K1 Parking garage 0 up to 6
MALE
K2 Private garage 1 per 7-20 Service sink:
1 per 25 1 per 25
K3 Repair garage 2 per 21-45 1 per floor.
3 per 46-70
FEMALE - 1 per 100
4 per 71-100
1 per 15 1 per 25 Add@ 3% per 101-200 and @ 2.5% per over 200
L Utility
L Utility 1 minimum 1 minimum - - - -
M Miscellaneous
M1 Special - - - - - -
structures****
- 1 minimum - - - -
M2 Fences, tanks
and towers
* Some of the water closets may be of European style. The water closet(s) shall not be oriented in the east-2est direction.
** The urinal(s) shall not be oriented in the east-west direction.
*** Toilet(s) of public use shall have at least one water tap with adequate drainage arrangement per ablution purpose when the numbers of devotees exceed twenty.
**** Plumbing fixture requirements for occupancy M1 shall be assessed considering its nature of use and the similarity in purpose with any of the occupancies mentioned above.
Table 8.6.2: Sanitary Appliance Minimum Internal Diameter of Waste Outlet (mm)
Soil appliances Waste appliances
(a) Indian and European type water 100 (a) Drinking fountain 25
closets
(b) Bed pan washers and slop sinks 100 (b) Wash basin 32
(c) Urinal with integral traps 75 (c) Bidets 32
(d) Stall urinals (with not more 40 (d) Domestic sinks and baths 40
than 50- 120 mm of channel
drainage)
(e) Lipped small urinal 40 (e) Shower bath trays 40
(f) Domestic bath tubs 50
(g) Hotel and canteen sinks 50
(h) Floor traps (outlet diameter) 65
6.7 Materials and Appliances
Different sanitary appliances, materials and fittings shall conform to the requirements of the Standards as provided in Tables 8.6.3 of this Chapter and Table 8.5.9 of Chapter 5 Part 8. For other appliances, materials and fittings that are not listed in the above mentioned Tables shall be subject to the approval of the Authority.
Table 8.6.3(a): Recommended Standards for Sanitary Appliances
Appliances Standard Appliances Standard
Ceramic wash basin and BDS 1162-87 Metal sink for domestic BS 1244
pedestals purpose
Ceramic wash down BS 1213 Urinals (bowl type) BDS 1163-87
water closet pans vitreous china part 1, 3
Foot rest vitreous china BDS 1163-87 Wash-down water closet BDS 1163-87
part 1, 4 pans, vitreous china part 1, 2
Integrated squatting pans BDS 1163-87 Water closet seat BS 1254
vitreous china part 1, 5 plastic
Metal hand rinse basin BS 1329 Water closet flushing BS 1125
cisterns and pipes
Table 8.6.3(b): Recommended Standards for Building Drainage and Vent Pipe
Material Standards
Acrylonitrile butadiene styrene ASTM D2661, ASTM F 628
(ABS plastic pipe)
Aluminum tubing ASTM B429, ASTM B745M
Brass pipe ASTM B43
Cast iron pipe ASTM A74
Copper or Copper-alloy tubing ASTM B75M, ASTM B88M, ASTM
B251M, ASTM B306
Galvanized steel pipe ASTM A53
Polyvinyl chloride plastic pipe ASTM D2665, ASTM D2949, ASTM F891
Table 8.6.3(c): Recommended Standards for Building Sewer or Building Storm
Sewer Pipe
Material Standards
Acrylonitrile butadiene styrene ASTM D2261, ASTM D2751, ASTM
(ABS plastic pipe) F628, ASTM D2321
Bihuminized fibre pipe ASTM D1861, ASTM D1862
Cast iron pipe ASTM A74
Concrete pipe ASTM C14M, ASTM C76M
Copper or Copper-alloy tubing ASTM B75, ASTM B88M, ASTM
B251M
Unplasticized Polyvinyl chloride (uPVC) ASTM D2665, ASTM D2949, ASTM
plastic pipe D3034, ASTM D2321, ASTM F891
Vitrified clay pipe ASTM C4, ASTM C700
Table 8.6.3(d): Recommended Standards for Subsoil Drainage Pipe Material Standard
Bituminous fibre pipe ASTM D2311 Cast iron pipe ASTM A74 Concrete pipe ASTM C654 M Polyethyline (PE) plastic pipe ASTM F405 Unplasticiged Polyvinyl chloride (uPVC) ASTM D2729, ASTM F891 plastic pipe Vitrified clay pipe ASTM C4, ASTM C700
Table 8.6.3(e): Recommended Standards for Joints between Different Pipes and Fittings
Material Standard
ABS plastic pipe and fittings ASTM D2235, ASTM D2661, ASTM
D3212, ASTM F628 ASME B1.20.1
Aluminium tubing ASTM C564
Asbestos cement pipe and fittings ASTM D1869
Brass pipe and fittings ASME B1.20.1
Cast iron pipe and fittings ASTM C564
Concrete pipe and fittings ASTM C443
Copper or Copper-alloy pipe and fittings ASTM B32, ASME B1.20.1
Copper-alloy tubing and fittings ASTM B32
CPVC plastic pipe and fittings ASTM F493, ASME B1.20.1
Galvanized steel pipe and fittings ASME B1.20.1
PE plastic pipe and fittings ASTM D2657
PVC plastic pipe and fittings ASTM D2657, ASTM D2855, ASTM
D3139, ASTM D3212, ASTM F402,
ASTM F656, ASME B1.20.1
Vitrified clay pipe and fitting ASTM C425
6.8 Hangers and Support and Pipe Jointing
6.8.1 Hangers and Support
The piping, fixtures and equipment used for plumbing, water supply and drainage system shall be provided with hangers and support in accordance with Sec 5.13 in Chapter 5.
6.8.2 Pipe Joints
The joints between different piping and fittings shall conform to the standards cited against them in Table 8.6.3. The requirements for the joints not specified in the table shall be subject to the approval of the Authority.
6.9 Design Considerations
6.9.1 Objective
For the design of drainage and sanitation system of different buildings according to building classification, the objective shall be to safeguard against fouling, deposition of solids and clogging and with adequate cleanouts and inspection chambers so arranged that the drains may be readily cleaned without the risk of health hazard.
6.9.2 General
(a) The plumbing system shall be designed and adjusted to use the minimum quantity of water consistent with proper performance and cleaning.
(b) Plumbing fixtures, devices and appurtenances shall be supplied with required volume of water at pressures adequate to enable these to function properly and without undue noise under normal conditions of use.
6.9.3 Different Building Drainage Systems
For the design and installation for drainage piping, one of the following building drainage systems shall be adopted: (i) single stack system; (ii) one-pipe system, and (iii) two-pipe system.
(a) Single stack system may be used with 100 mm diameter stack for buildings up to 5-storey height. The fixtures in each floor shall be connected to a single stack for increasing the rate of discharge in the downward direction. The recommended depth of water seal trap for different fixtures shall be in accordance with Table 8.6.4. There shall be at least 200 mm vertical distance between the waste branch and the soil branch connection, while the soil pipe will be connected to stack above the waste pipe. The size of soil branch shall not be less than 100 mm. The horizontal branch distance for fixtures from stack and bend(s) at the foot of stack to avoid back pressure as well as the vertical distance between the lowest connection and the invert of drain shall be as shown in Figure 8.6.1.
(b) Where all types of waste from the building are desired to be discharged into a common sewer or into same waste disposal system, one pipe system may be used (Figure 8.6.2).
(c) Where the sullage from kitchen and bath will be dealt with separately and where soil waste shall be discharged into septic tank or Imhoff tank, the two pipe system shall be used (Figure 8.6.3).
Table 8.6.4: Recommended Depth of Water Seal Trap for Different Fixtures
Fixture Water Seal (mm) Water Closets 50 Floor Traps 50 For Waste Branch of 75 mm diameter or More 40 For Waste Branch of Less Than 75 mm diameter 75
6.9.4 Water Closet Compartment for Physically Handicapped
6.9.4.1 Provision for Wheelchair Users
The water closet compartment for wheelchair users shall have at least the dimensions and fittings as shown in Figure 8.6.4.
6.9.4.2 Provision for Ambulant Disabled People
The minimum dimension for water closet compartment and the fittings for ambulant disabled people shall be as shown in Figure 8.6.5.
6.9.5 Installation of Drainage System
6.9.5.1 All plumbing fixtures shall be made of smooth and nonabsorbent materials, free from concealed fouling surfaces and may be located in ventilated enclosures.
6.9.5.2 Whenever possible, all drainage system shall be drained to the public sewer or private waste disposal system by gravity. Horizontal drainage piping up to 75 mm diameter shall be installed with a fall of not less than 20 mm/m and for larger than 75 mm diameter the fall shall not be less than 10 mm/m. It is a good policy to design the system for the highest possible velocity. However, consideration should be given to the fact that the high velocities in pipes with slopes greater than 20 mm per m may cause self-siphoning of trap seal.
6.9.5.3 Where conditions do not permit building drains and sewers to be laid with a fall as great as that specified, a lesser slope may be permitted provided the computed velocity in the drains will not be less than 0.6 m per second. The maximum recommended velocity will be 2.5 m per second.
6.9.5.4 Soil pipe conveying any solid or liquid filth to a drain shall be circular with a minimum dia of 100 mm. The waste branch from bath room, wash basin or sink shall be of 32 mm to 50 mm diameter and shall be trapped immediately beneath such wash basins or sink by an efficient siphon trap with adequate means of inspection and cleaning. The minimum recommended size of waste stack is 75 mm.
6.9.5.5 The soil and waste stack shall be continued upward undiminished in size 0.6 m above the roof surface when the roof will be used only for weather protection. Where the roof will be used for any purpose other than weather protection, the soil and vent stack shall run at least 2 m above the roof surface so that there shall be least possible nuisance.
6.9.5.6 Soil and waste stack shall be firmly attached to the wall with a minimum clearance of 25 mm from wall.
All soil, waste, vent (ant siphoning) stacks shall be covered on top with cowl of same pipe material.
Figure 8.6.1 Single stack system
Figure 8.6.2 Diagram of one - pipe system
Figure 8.6.3 Diagram of two pipe system
Figure 8.6.4 Water closet compartment for wheelchair user
Figure 8.6.5 Water closet stall for ambulant disabled people
Figure 8.6.6 Circuit vent for a battery of water closets
6.9.6 Installation of Venting System
6.9.6.1 The vent stack or main vent shall be installed in conjunction with a soil or waste stack in a building. One vent stack may serve not more than two soil or waste stacks.
6.9.6.2 Ventilating pipes should be so installed that water cannot be retained in them. They should be fixed vertically. Whenever possible, horizontal runs should be avoided. Ventilating pipe shall be carried to such a height and in such a position as to afford by means of the open end of such pipe or vent shaft, a safe outlet for foul air with the least possible nuisance.
6.9.6.3 The building with building drain shall have at least one 100 mm vent stack or stack vent carried full size to outdoor air above the roof in accordance with Sec 6.9.5.7 above.
6.9.6.4 The diameter of a vent stack shall not be less than 50 mm.
6.9.6.5 The diameter of a branch vent pipe on a waste pipe shall not be less than 25 mm or two-thirds of the diameter of the branch waste pipe ventilated.
6.9.6.6 The branch vent pipe on a soil pipe shall not be less than 32 mm in diameter.
6.9.6.7 All main vents or vent stacks shall connect full size at their base to the building drain or to the soil or waste stack at or below the level of the lowest drainage connection to them. All vent stacks shall extend undiminished in size above the roof or shall be reconnected to a vent header or to the stack vent portion of the soil or waste stack, at least 150 mm above the flood level of the highest fixture connection discharging into the soil or waste stack. Where the roof is to be used for any purpose other than weather protection, the vent extension shall be in accordance with the Sec 6.9.5.7.
6.9.6.8 In case of offsetting of stacks a relief vent shall be provided at the base of upper stack just above the start of offset and at top of the lower stack portion just below the end of offset.
6.9.6.9 In high rise buildings yoke vent shall be provided at 10 storey intervals counting down from top.
6.9.6.10 In case huge number of fixtures are installed in battery to a single branch drainage pipe, circuit or loop vents shall be provided after 8 fixtures interval for 100 mm drain pipe and 24 fixtures interval for 150 mm drain pipe as shown in Figure 8.6.6 6.9.6.11 Offset in the stack vent portion of soil or waste stack, offset in vent stack and connection of vent stack at the bottom to soil or waste pipe or to the building drain shall be at an angle of at least 45o to the horizontal.
6.9.6.12 All vent and branch vent pipe shall be so graded and connected that sufficient slope is provided for condensation to drain back to soil or waste pipe by gravity.
6.9.6.13 Where fixtures, other than water closets discharge into the stack downstream of a water closet, each fixture connecting downstream shall be individually vented.
6.9.6.14 Soil and waste stacks in a building having more than 10 branch intervals shall be provided with a relief vent (Figure 8.6.7) at each tenth interval counting from the top floor.
6.9.6.15 In case the adjoining building is taller, the ventilating pipe shall be carried higher than the roof of the adjacent building, wherever it is possible.
6.9.6.16 The building drain intended for carrying waste water and sewage from a building shall be provided with at least one ventilating pipe situated as near as practicable to the building and as far away as possible from the point at which the drain empties in to the sewer or other earner.
6.9.7 Clearance of Blockages
6.9.7.1 There shall be sufficient and suitable access points at every change of alignment, gradient or diameter or at bends and junctions for clearing blockages from drains which cannot be reached by any other means.
6.9.7.2 In case of straight run of pipes, access points shall be provided at intervals of 15 meter. Tables 8.6.5 and 8.6.6 show the maximum spacing and the recommended minimum dimensions for access fittings and chambers for the specified depth.
Figure 8.6.7 Relief vents for stack of more than ten branch intervals
Table 8.6.5: Maximum Spacing of Access Points
From To Access To Junction To Inspection To
Fitting (m) Chamber Manhole
(m) (m) (m)
Start of external drain 12 - 22 45
Rodding eye 22 22 45 45
Access fitting † - 12 22 22
Inspection chamber 22 22 45 45
Manhole 22 - 45 90
† higher spacing may be used for larger size access fitting.
Table 8.6.6 Minimum Dimensions for Access Points
Access Points Depth (m) Internal Sizes Cover Sizes
Length x width Diameter Length x width Circular
(mm x mm) (mm) (mm x mm) (mm)
Rodding eye min. 100 mm or size of drains
Access fitting 0.6 or less 150 x 100 150 150 x 100 150
Inspection 1.0 or less 450 x 450 450* 450 x 450 450*
chamber
Manhole 1.5 or less 1200 x 750 1050 600 x 600 600
over 1.5 1200 x 750 1200 600 x 600 600
over 2.7 12000 x 840 1200 600 x 600 600
* 190 mm dia may be used for depth ≤ 0.6 m
6.9.7.3 Access should be one of the following four types :
(i) Rodding eyes - capped extensions of the pipes,
(ii) Access fittings - small chambers (or an extension of the pipes) but not with an open channel,
(iii) Inspection chambers - chambers with working space at ground level, and
(iv) Manholes - large chambers with working space at drain level.
6.9.7.4 Inspection chambers and manholes shall have removable non-ventilating covers of durable material and be of suitable strength. Inspection chambers and manholes in buildings shall have mechanically fixed airtight covers unless the drain itself has watertight access covers. Manholes deeper than 1 m shall have non-corrosive steps or fixed ladders. Figures 8.6.8 and 8.6.9 show the details of typical manholes at smaller depth (<1 m) and at higher depth (>1 m) respectively. Figure 8.6.9 shows the details of a drop manhole. The drop manhole is a manhole that serves as a junction and receives sewer lines at two different elevations.
6.9.7.5 Spacing of manholes
The spacing of manholes for a given pipe size should be as follows :
Pipe Diameter (mm) Spacing of Manhole (m)
Up to 300 45
301 to 500 75
501 to 900 90
Beyond 900 Spacing shall depend upon local condition and shall
be gotten approved by the Authority
Figure 8.6.8 Detail of Manhole (Depth 1m and Below)
Figure 8.6.9 Detail of manhole (depth more than 1 m) 6.9.8 Protection Against Rodent Holes through walls shall be such that they will not provide passage of rodent or other insects from room to room or from floor to floor. Materials used for embedding pipes shall be rodent proof.
6.9.9 Bedding and Backfilling
The choice of bedding and backfilling depends on the depth of the bed, and size and strength of the materials. Table 8.6.7 and Figure 8.6.10 show two types of bedding and backfilling, and minimum and maximum depth of cover for each type of bedding for rigid pipings. The bedding and backfilling for flexible pipings is shown in Figure 8.6.11. The minimum depth of bedding for flexible pipings shall be 0.3 m where there will be no extra surcharge load coming on pipe other than back filling.
The depth shall not be more than 10 m. The flexible pipe may be laid with less cover in fields and gardens. The bedding and backfilling shall be in accordance with Figure 8.6.12.
Table 8.6.7: Limits of Cover (m) for Standard Strength Rigid Pipes in any Width of Trench
Pipe Bore Bedding Fields and Gardens Light Traffic Heavy Traffic Road
Class Roads
(mm) Min Max Min Max Min Max
100 Type 1 0.3 7.4 0.4 7.4 0.4 7.2
Type 2 0.3 5.8 0.5 5.8 0.5 5.5
150 Type 1 0.6 5.0 0.6 5.0 0.6 4.6
Type 2 0.6 3.9 0.7 3.8 0.7 3.3
Figure 8.6.10 Drop manhole
Figure 8.6.11 Bedding for rigid pipes (a) (b)
Figure 8.6.12 (a) Bedding for flexible pipes; (b) Flexible pipes bedding under concrete slab
6.9.10 Grease Traps
Oil and grease is found in wastes generated from kitchens in hotels, industrial canteens, restaurant, butcheries, some laboratories and manufacturing units having a high content of oil and greases in their final waste.
Waste exceeding temperature of 60° C should not be allowed in the grease trap. When so encountered it may be allowed to cool in a holding chamber before entering the grease trap.
Oil and greases tend to solidify as they cool within the drainage system. The solidified matter clogs the drain sand the other matter in the waste stick to it due to the adhesion properties of the grease. Oil and greases are lighter than water and tend to float on the top of the waste water.
Grease traps shall be installed in building having the above types of wastes. In principle the grease laden water is allowed to retain in a grease trap which enables any solids to be settled or separated for manual disposal. The retention time allows the incoming waste to cool and allow the grease to solidify. The clear waste is then allowed to discharge into the building’s drainage system.
6.9.11 Oil Interceptors
Oils and lubricants are found in wastes from vehicle service stations, workshops manufacturing units whose waste may contain high content of oils. Oils, for example, petroleum, kerosene and diesel used as fuel, cooking, lubricant oils and similar liquids are lighter than water and thus float on water in a pipe line or in a chamber when stored. Such oils have a low ignition point and are prone to catch fire if exposed to any flame or a spark and may cause explosion inside or outside the drainage system. The flames from such a fire spread rapidly if not confined or fire vented at the possible source. Lighter oils and lubricants are removed from the system by passing them through an oil interceptor/petrol gully. They are chambers in various compartments which allow the solids to settle and allow the oils to float to the top. The oil is then decanted in separate containers for disposal in an approved manner. The oil free waste collected from the bottom of the chamber is disposed in the building drainage system.
6.9.12 Septic Tank
6.9.12.1 Septic tank (Figures 8.6.13 and 8.6.14) discharging into either a subsurface disposal field or one or more seepage pits shall be required for the approval of drainage and sanitation plans for the places where public sewers are not available.
Figure 8.6.13 Typical one chamber brick septic tank
Figure 8.6.14 Typical two chamber concrete septic tank
6.9.12.2 Such disposal method shall be designed by a licensed professional in accordance with the requirement of the provisions of this Code and regulations of the concerned authorities.
6.9.12.3 The design of such system shall be on the basis of location with respect to wells or other sources of water, soil permeability, ground water elevation, area available and maximum occupancy of the building.
6.9.12.4 Sullage water shall not be discharged into the septic tank.
6.9.12.5 Effluent from septic tank(s) shall not discharge into open water courses.
6.9.12.6 The minimum distance for various components of the disposal system shall be in accordance with Table 8.6.8.
6.9.12.7 The flow into a septic tank may be calculated on the basis of plumbing fixtures discharging soil wastes simultaneously into it. The capacity of septic tank for residential buildings shall be determined according to the formula in Appendix S. For other occupancies a reduction factor shall be used as shown in Appendix S.
6.9.12.8 The septic tank shall have a minimum liquid capacity of 2000 liters, minimum width 1 m and minimum liquid depth 1 m. The minimum length of a septic tank shall be at least thrice its width. It is recommended that the maximum length of a septic tank shall be not more than 4 times its width.
6.9.12.9 The maximum size of a septic tank shall be limited to the number of users not exceeding 300 persons for residential buildings.
6.9.12.10 The volume required for digested sludge and scum may be computed on the basis of 0.04 m3/capita/ year. There shall be a clearance between top of the liquid level and bottom of the tank cover slab which shall be at least 300 mm.
6.9.12.11 The liquid retention time of a septic tank shall be at least 1 day.
6.9.12.12 The desludgging frequency of a septic tank shall be at least 6 months interval and maximum once a year.
6.9.12.13 It is recommended to use a two chamber septic tank when the capacity of a septic tank exceeds 3000 liters. The inlet compartment of a two chamber septic tank shall have a capacity not less than two-third of its total capacity (Figure 8.6.14).
Table 8.6.8: Location of Components of Sewage Disposal System
System Distance (m)
Component Building Foundation Well Stream Seepage Pit Dry Well
Septic tank 1.5 8 - 1.5 - Disposal field 3 15 7.5 6 6 Seepage pit 4.5 15 15 6 6 Dry well 3 15 - 6 -
6.9.12.14 The septic tank shall be constructed of corrosion resistant material and be of permanent water tight construction. The manhole cover and the roof of the tank shall be designed for at least 7 kPa live load. The inlet compartment shall be provided with a manhole. Outlet compartment shall also be provided with a manhole. The design guideline of a septic tank is presented in Appendix S.
6.9.13 Imhoff tank(s)
6.9.13.1 Imhoff tank (Figure 8.6.15) discharging into either a subsurface disposal field or one or more seepage pits shall be required for the approval of drainage and sanitation plans for the places where public sewers are not available.
6.9.13.2 Imhoff tank shall be used where more than 300 peoples of residential buildings are to be served.
6.9.13.3 The settling chamber shall be designed for a detention period of 1.5 to 4.0 hours and an over flow rate of 0.95 to 1.4 m/hr. The displacement velocity should not be more than 18 m/hr. Sloping sides of settling chamber shall have inclination 1.0 horizontal to 1.2 vertical. The slot at the bottom is 0.15 to 0.25 meter measured along the slope of the hopper. The width of the side spaces should not be less than 0.45 meter. The digestion chamber should have a capacity to store about 6 to 12 months digested sludge. Capacity of the digestion chamber can be found from the following formula- (8.6.1)
Where, is the volume of the digestion tank in m3/capita below the neutral zone which is 0.2 m below the slot. is the volume of fresh sludge in m3/capita/day and is the volume of the digested sludge in m3/capita/day and t is the time required for digestion. The digestion chamber should have sloping side with a ratio of 4 horizontal to 5 vertical.
6.9.13.4 The Capacity found in Sec. 6.9.12.3 is true for residential buildings. For other occupational buildings use a reduction factor as shown in Appendix S.
Figure 8.6.15 Cross section of an imhoff tank
6.9.14 Installation
Septic and Imhoff tanks shall be located with a horizontal distance not less than specified in Table 8.6.9 between various elements. Tanks installed in ground water shall be securely anchored. Three inch (75 mm) thick compacted bedding shall be provided for all septic and other treatment tank installations. The bedding material shall be sand, gravel, granite, lime rock or other noncorrosive materials of such size that the material passes through a 0.5 inch (12.5 mm) screen.
Table 8.6.9: Minimum horizontal separation distances for treatment tanks element distance Elements Distance (m) Elements Distance (m)
Building 1.5 Reservoir 7.5 Cistern 7.5 Spring 15 Foundation wall 1.5 Stream or watercourse 7.5 Lake, high water mark 7.5 Swimming pool 4.5 Lot line 0.6 Water service 1.5 Pond 7.5 Well 7.5
Each cleanout shall be installed so that it opens to allow cleaning in the direction of flow of the soil or waste or at right angles thereto, and except in the case of Wye branch and end-of-line cleanouts, shall be installed vertically above the flow line of the pipe.
The bath tub shall be fitted with overflow and waste pipe of nominal diameter of not less than 32 mm and 40 mm respectively.
6.9.15 Disposal Field and Seepage Pit
6.9.15.1 A distribution box shall be provided to receive the effluent from the septic tank or Imhoff tank to assure equal distribution to each individual line of disposal field. The distribution box shall be connected to the septic tank or Imhoff tank by a watertight sewer line and shall be located at the upper end of disposal field. Figure 8.6.16 shows the plans and sections of typical distribution boxes.
6.9.15.2 Soil percolation tests (at least for three holes) shall be performed at the site of a proposed individual sewage disposal system installation to determine the suitability of soil and site.
6.9.15.3 The liquid capacity (volume below inlet line) of seepage units (disposal field or seepage pit) shall be at least twice that of a septic tank or Imhoff tank. Effective absorption area of seepage unit may be computed in accordance with Table 8.6.10.
6.9.15.4 No seepage unit shall be extended into water table directly. The bottom of seepage unit shall be at least 1 meter above the highest water table.
6.9.15.5 Each disposal field shall have at least two outlet distribution lines from the distribution box. No portion of disposal field shall be installed under any pavement or any area where there will be vehicular traffic or parking 6.9.15.6 Minimum standards for disposal field construction shall be as shown in Table 8.6.11.
6.9.15.7 Seepage pit (soak pit) shall be lined with stone, brick or concrete blocks laid up dry with open joints that are backed up with at least 75 mm coarse aggregate. The joints above the inlet shall be sealed with cement mortar. A reinforced concrete cover shall be provided. For cover area more than 0.75 m2 the pit shall have an access manhole. The bottom of the pit shall be filled with coarse gravel, or crushed stone/brick to a depth of 300 mm. Figure 8.6.17 provides the details of a seepage pit.
6.9.15.8 Large dry well shall be constructed in accordance with the requirements for seepage pit (Sec 6.9.12). However, for small dry wells handling limited quantities of waste water the pit may consist of a 2.0 m deep and 1.0 m diameter pipe filled with crushed bricks/stone, Figures 8.6.18 and 8.6.19.
6.9.15.9 French drains may be employed as surface water drains for drainage of unpaved surfaces.
Figure 8.6.16 Distribution boxes
Table 8.6.10: Absorptive Capacity of Disposal Field and Seepage Pit
Percolation Test Rate in Effluent Allowance Rate of Seepage Unit
Minutes for Water to Fall 25 (l/m2/day)
mm Disposal Field Seepage Pit (wall area)
Trenches
(bottom of trench)
2 or less 128 172
5 96 128
10 68 92
30 32 44
60 (not recommended) 16 24
over 60 (not suitable) - -
Table 8.6.11: Design Features of Disposal Field
Design Items Requirements
Number of lateral branches 2
Maximum length of branch 20 m
Minimum diameter of field distribution pipe 100 mm
Maximum slope of field distribution pipe 3.3 mm per m
Depth of trench 0.45 m to 9 m
Trench bottom, minimum above ground water 0.61 m
Trench bottom width 0.45m to 0.75m
Depth of coarse material
under pipe 150 mm
over pipe 50 mm
Size of coarse material 12 mm to 63 mm
Figure 8.6.17 Typical seepage pit Figure 8.6.18 Typical location of a dry wall
Figure 8.6.19 Installation details of a dry wall
6.10 Design of Drainage and Sanitation System
6.10.1 Estimation of Maximum Load Weight of Waste Water
To estimate the total load weight carried by a soil or waste pipe, the relative load weight for different kinds of fixtures are provided in Table 8.6.12. Table 8.6.13 provides an approximate rating of those fixtures not listed in Table 8.6.12.
Table 8.6.12: Fixture Units for Different Sanitary Appliances or Groups
Type of Fixture Fixture Unit Value
as Load Factor
One bathroom group consisting of water closet, wash basin and
bath tub or shower stall :
a) Flush Tank water closet 3
b) Flush-valve water closet 6
Bathtub* 2
Bidet 2
Type of Fixture Fixture Unit Value
as Load Factor
Combination sink and tray (drain board) 2
Drinking fountain 0.5
Floor traps† 1
Kitchen sink, domestic 2
Wash basin, ordinary‡ 1
Wash basin, surgeon's 2
Shower stall, domestic 2
Shower (group) per head 3
Urinal, wall hung 4
Urinal, stall 4
Water closet, tank operated 3
Water closet, valve operated 6
* A shower head over a bath tub does not increase the fixture unit value.
† Size of floor trap shall be determined by the area of surface water to be drained.
‡ Wash basin with 32 mm and 40 mm trap have the same load value.
Table 8.6.13: Fixture Unit Values for Fixtures Based on Fixture Drain or Trap Size
Fixture Drain on Trap Size Fixture Unit Value
30 mm and smaller 1
40 mm 2
50 mm 3
65 mm 4
75 mm 5
100 mm 6
6.10.2 Gradient and Size of Pipe
6.10.2.1 The building drains and sewer shall be designed to discharge the peak simultaneous load weight flowing half-full with a minimum self-cleansing velocity of 0.75 m per second. However, flatter gradient may be used if required but the minimum velocity shall not be less than 0.6 m per second. Again, it is undesirable to employ gradients giving a velocity of flow greater than 2.5 m per second.
6.10.2.2 The maximum number of fixture units that may be connected to a given size of building sewer, building drain, horizontal branch or vertical soil or waste stack is provided as in Tables 8.6.14 and 8.6.15.
6.10.3 Size of Vent Piping
6.10.3.1 The size of vent piping shall be determined from its length and the total number of fixture units connected thereto in accordance with Table 8.6.16.
6.10.3.2 The branch vent shall be sized in accordance with Table 8.6.17.
Table 8.6.14: Maximum Number of Fixture Units that can be connected to Branches and Stacks
Diameter Any One Stack of 3 More than 3 Storeys in Height
of Pipe Horizontal Storeys in Height Total Total at One Storey
(mm) Fixture or 3 Intervals for or Branch Interval
Brancha Stack
30 1 2 2 1
40 3 4 8 2
50 6 10 24 6
65 12 20 42 9
75 20 30 60 16
100 160 240 500 90
125 360 540 1100 200
150 620 960 1900 350
200 1400 2200 3600 600
250 2500 3800 5600 1000
300 3900 6000 8400 1500
375 7000 b b b
a b
Does not include branches of the building sewer. Sizing load based on design criteria
Table 8.6.15: Maximum Number of Fixture Units that can be connected to Building Drains and Sewers
Diameter Maximum Number of Fixture Units that can be Connected to any
of Pipe Portion* of the Building Drain or the Building Sewer for Various
(mm) Slopes
1/200 1/100 1/50 1/25
100 - 180 216 250
150 - 700 840 1000
200 1400 1600 1920 2300
250 2500 2900 3500 4200
300 2900 4600 5600 6700
375 7000 8300 10000 12000
* Includes branches of building sewer
6.11 Construction Relating to Conveyance of Sanitary Wastes
6.11.1 Conveyance of Sanitary Wastes
6.11.2 The layout of drainage systems shall be simple. Change of direction and gradient shall be minimized and shall be as easy as practicable.
6.11.3 The excavation, where necessary, shall be made in accordance with Table
8.6.18.
6.11.4 The depth of cover shall be in accordance with Sec 6.9.9.
6.11.5 The pipe shall be laid to even gradients and change of gradient shall be combined with an access point (Sec 6.10.2). However, access points shall be provided only if blockages could not be cleared without them.
6.11.6 The joints and connection in drainage and venting system shall be gastight and watertight for the pressures required by the test, with the exception of those portions of perforated or open joint piping which will be installed for the purpose of collecting and conveying ground or seepage water to the underground storm drains.
6.11.7 Piping in drainage and venting system shall be installed without undue strains and stresses and provision shall be made for expansion, contraction and structural settlement. Vertical piping shall be secured at sufficiently close intervals to keep the pipe in alignment and carry the weight of the piping and its content. The horizontal piping shall be supported at sufficiently close intervals to keep it in alignment and to prevent sagging.
Table 8.6.16: Size and Length of Vent Stacks and Stack Vents
Diameter of Total Fixture Maximum Development Length of Vent (m)*
Soil or Unit for Diameter (mm) of Vent Pipes
Waste Stack Connected to
30 40 50 65 75 100 125 150 200 250 300
(mm) fixture
30 2 9
40 8 15 45.5
40 10 9 30.5
50 12 9 22.5 61
50 20 8 15 45.5
65 42 9 30.5 91.5
75 10 12.5 45.5 109.5 317
75 21 9.5 33.5 82 247
75 53 8 28.5 70 207
75 102 7.5 26 64 189
100 43 10.5 26 76 298.5
100 140 8 19.5 61 228.5
100 320 7 16.5 52 195
100 540 6.5 15 45.5 176.5
125 190 8.5 25 97.5 301.5
125 490 6.5 19 76 231.5
125 940 5.5 16 64 204
125 1400 4.5 15 58 180
150 500 10 39.5 122 305
Diameter of Total Fixture Maximum Development Length of Vent (m)*
Soil or Unit for Diameter (mm) of Vent Pipes
Waste Stack Connected to
30 40 50 65 75 100 125 150 200 250 300
(mm) fixture
150 1100 6.5 30.5 94.5 237.5
150 2000 6 25.5 79 201
150 2900 23.5 73 183
200 1800 9.5 29 73 286.5
200 3400 7 22 58 219.5
200 5600 6 19 48.5 186
200 7600 5.5 17 42.5 170.5
250 4000 9.5 23.5 94.5 292.5
250 7200 7 18 73 225.5
250 11000 6 15.5 61 192
250 15000 5.5 14 55 173.5
300 7300 9.5 36.5 116 286.5
300 13000 7 28.5 91.5 219.5
300 20000 6 24 76 186
300 26000 5.5 22 70 152.5
375 15000 12 39.5 94.5
375 25000 9.5 29 73
375 38000 8 24.5 61
375 50000 7 22.5 55
* The development length shall be measured from the vent connection to the open air
Table 8.6.17: Minimum Diameter and Maximum Length of Individual, Branch, and Circuit Vents for Horizontal Drainage Branches
Diameter of Slope of Maximum Development
Horizontal Horizontal Length of Vent (m) for Diameter (mm) of Vent Pipe
Drainage Branch Drainage
(mm) Branch (mm/m) 30 40 50 65 75 100 125 150 200 250
30 20 NL*
40 NL
40 20 NL NL
40 NL NL
50 10 NL NL NL
20 88 NL NL
40 45 115 NL
65 10 54 137 NL
20 29 73 NL NL
40 15 39 NL NL
75 10 - 58 NL NL NL
20 29.5 128 NL NL
40 15 67 NL NL
100 10 - 58 NL NL NL
20 30 94 NL NL
40 14.5 48.5 125 NL
125 10 149 NL NL
20 58 76 NL NL
40 29.5 39.5 NL NL
150 10 NL NL NL
20 14 58 76 NL NL
40 29.5 39.5 NL NL
200 10 NL NL NL
20 14 58 94.5 NL NL
40 27.5 45.5 125 NL NL
Diameter of Slope of Maximum Development
Horizontal Horizontal Length of Vent (m) for Diameter (mm) of Vent Pipe
Drainage Branch Drainage
(mm) Branch (mm/m) 30 40 50 65 75 100 125 150 200 250
250 10 152 NL NL
20 11.5 58 73 NL NL
40 26 33.5 NL NL
300 10 9.5 54.5 NL NL
20 24 128 NL
40 8 61 NL
* NL means no limit; Actual value in excess of 150 m.
Table 8.6.18: Minimum Width at Bottom of Trench
Depth of Trench (m) Width of Trench (m)
Up to 1.2 Diameter of pipe plus 0.4
Above 1.2 Diameter of pipe plus 0.45
Note: Trench top width shall not be less than 0.75 m for depths exceeding 0.9 m
6.12 Refuse Chute System
6.12.1 All buildings higher than 6-storeys shall be provided with refuse chute system for transporting and collecting refuse from different floors in a sanitary way. The refuse shall be received from the respective floor through an inlet hopper in to the chute which conveys refuse and discharges into the collection chamber. The refuse from the collection chamber shall be cleared at suitable intervals.
6.12.2 The refuse chute, inlet hopper and collection chamber shall be constructed with smooth and nonflammable materials.
6.12.3 The hopper shall be self-cleaning and shall be fitted with self-closing shutter to prevent the passage of foul gases inside the building.
6.12.4 The diameter of the chute shall not be less than 300 mm. It shall be adequately ventilated at the top. The chute shall be provided with suitable arrangements for flushing with water for the full length.
6.13 Basement Floor Drainage System
6.13.1 All buildings having basement floor below the surrounding sewer system and area more than 1000 m2 shall have pumping system to drain out wastewater.
6.13.2 All buildings having basement floor below the surrounding sewer system and area more than 1000 m2 shall have one sump pit for every 1000 m2.
6.13.3 For more than one sump pit, pits shall be connected to a master sump pit from where pumping shall be done to drain out the waste. Minimum diameter of sump pit connection drain pipe shall be 75 mm.
6.13.4 For wastewater and sewage drainage from basement floor separate drainage system shall be provided.
6.13.5 The collection chamber shall be of suitable size and located at ground level.
6.13.6 The design and arrangement of the system shall be in accordance with established engineering practices.
6.14 Health Care Drainage System
6.14.1 General
The health care drainage system shall comply with applicable drainage and venting requirements specified in this Chapter and with this Section.
6.14.2 Special Fixtures and Equipment
The hospital shall be provided with clinical sink, bedpan washer and such other fixtures and equipment for disposal of bedpan contents and for the cleansing and disinfection of such fixtures. A clinical sink shall not be considered as a substitute for service sink.
6.14.3 Bedpan Washer and Clinical Sink
Bedpan washer and clinical sink shall be connected to soil branches and soil stacks through a water seal trap. The bedpan washer with vapour vent connection shall be provided with additional local vent stack. The minimum vent stack size for bedpan washer shall be in accordance with Table 8.6.19.
Table 8.6.19: Minimum Vent Stack Size in Bedpan Drainage
No of Bedpan Washer Diameter (mm) Up to 3 bedpan washers at different floors 50 4 to 6 bedpan washers 75 7 to 12 bedpan washers 100
The bottom of the bedpan local vent stack (except for one bedpan washer) shall be drained indirectly into sanitary drainage system through traps. The size of the trap and connecting pipe shall be at least the size of the vent stack. At least 6 mm diameter water supply piping shall be taken from each flush supply of each bedpan washer on the discharge side of vacuum breaker, trapped to form 75 mm or more trap seal and connected to the local vent stack on each floor.
6.14.4 Sterilizer Vent Stack
The pressure or non-pressure sterilizer shall have vent connection to the sterilizer vent stack. This vent connection shall be accessible for inspection and cleaning. The size of sterilizer vent stack shall be as follows:
6.14.4.1 Pressure sterilizers
The minimum diameter for pressure sterilizer vent stack shall be 63 mm. The stack size for combinations of pressure sterilizer exhaust shall be in accordance with Table 8.6.20.
Table 8.6.20: Pressure Sterilizer Vent Stack Size
Stack Size Number of Connections Permitted for Different Combination
( mm) Sizes (mm)
19 25 31 38
3 - - -
- 2 - -
38
- - 1 -
2 1 - -
6 - - -
- 3 - -
- - 2 -
50 - - - 1
3 2 - -
2 1 1 -
1 1 - 1
15 - - -
- 7 - -
- - 5 -
75
- - - 3
1 5 - 1
- 1 2 2
6.14.4.2 Pressure instrument washer sterilizers
The minimum size of sterilizer vent stack for instrument washer sterilizer shall be 50 mm for up to two sterilizers. The 75 mm stack will serve up to four sterilizers.
6.14.4.3 Non-pressure sterilizers
The minimum diameter of non-pressure sterilizer vent stack shall be 50 mm for utensil sterilizer and 38 mm for instrument sterilizer. Multiple installations shall be sized in accordance with Table 8.6.21.
6.14.4.4 Bedpan steamers
The diameter for one bedpan steamer shall be 38 mm. The stack size for combinations shall be in accordance with Table 8.6.21.
6.14.5 Vent Extension
The termination of vent stack shall be in accordance with Sections 6.9.5.6 and 6.9.6.7.
Table 8.6.21: Non-pressure Sterilizer Vent Stack or Bedpan Steamer Sizes
Stack Sizes No of Connections Permitted for Different
(mm) Connection Sizes(mm)
38 50
38 1 -
2 -
50 - 1
1 1
4 -
75 - 2
2 2
8 -
100 - 4
4 4
6.14.6 Special Fixture Drainage
The device, appurtenance and appliance required for special purposes such as refrigerators, ice boxes, cooling or refrigerating coils etc. shall be protected against backflow with adequate air gap between the equipment inlet and drainage outlet.
6.14.7 Mental Health Care Centre and Prisoners Cell
The pipes and traps used in mental health care buildings and prisoner cells shall not be exposed and all fixtures shall be securely bolted through walls.
6.15 Inspection, Testing and Completion Certificate
6.15.1 Inspection
The new drainage and sanitation system or part of the existing system shall not be covered or enclosed or put into operation until it has been inspected, tested and approved by the Authority. The Authority may examine the appliances and fittings before their installation or during the progress of the work. An installation of plumbing work, whether new or existing, which is found to be defective or unsafe shall not be allowed to continue in use unless corrections have been made to comply with the Code requirements.
6.15.2 Testing
6.15.2.1 Drainage and venting system
The piping of drainage and venting system shall be tested first with water. The final test of completed drainage and venting system may be done by smoke test. The water and smoke tests shall be performed as described below:
(a) Water Test: The water test shall be applied to the drainage and venting system either for the whole system or part (section) thereof. For the entire system, all openings in the piping except the highest opening shall be closed, and the system filled with water to the point of overflow. For the system to be tested in sections each opening shall be tightly plugged except the highest opening of the section under test and each section shall be filled with water but no section shall be tested with less than a 3 m head of water. In testing successive sections, at least the upper 3 m of the next preceding section shall be tested so that no joint or pipe in the building (except the top most 3 m of the system) shall have been submitted to a test of less than a 3 m head of water. The water shall be kept in the system or in the portion under test for at least 15 minutes before the inspection starts. The system or the part of the system under test shall be watertight at all points.
(b) Smoke Test: The final test for gas and water tightness of the completed drainage and venting system may be performed by smoke test. The test is performed by filling all traps with water and then introducing smoke into the system produced by one or more smoke machines. When the smoke appears at the stack openings on the roof, they shall be closed and a pressure equivalent to 25 mm head of water shall be built and maintained for 15 minutes before inspection starts.
6.15.2.2 Building sewer
The Connection between building sewer and public sewer or individual sewage disposal system shall be closed by inserting a test plug. The building sewer shall be filled with water under a pressure of not less than 30 kPa for at least 15 minutes. The system shall be able to maintain the test pressure.
6.15.3 Completion Certificate
After the installation of drainage and sanitation system, the licensed plumber shall give a completion certificate to the authority in a prescribed form (Appendix T) for inspection and testing. After testing, the Authority will give the final approval (as presented in completion certificate form, in the Appendix T) to use the system.
6.16 Guide to Maintenance
6.16.1 The drainage and sanitation system shall be maintained in a sanitary and safe operating condition by the owner or his designated agent. All device or safeguards required by the Code shall be maintained in working order.
6.16.2 The following operations shall be carried out during periodical cleaning of a drainage and sanitation system:
(a) The covers of inspection chambers and manholes shall be removed and the side benching and channels shall be scrubbed.
(b) All lengths of main and branch drains shall be rodded by means of drain rods and a suitable rubber or leather plunger. After rodding, the drains shall be thoroughly flushed with clean water.
(c) The ladders/rings in deep manholes and the manhole covers shall be painted.
(d) All surface drains shall be cleaned.
(e) All subsoil drains shall be examined for obstruction at the open joints.
(f) Refuse chute system shall be cleaned.
6.17 List of Related Appendices
Appendix Q Application for Permit to Construct Drainage and Sanitation System
Appendix R One-hour Rainfall
Appendix S Design Guideline of a Septic Tank Appendix T Completion Certificate (Drainage and Sanitation Works)
Source: Bangladesh National Building Code 2020, S.R.O. No. 55-Law/2020, Bangladesh Gazette (Extraordinary), 11 February 2021. Tables, figures and equations: refer to the linked gazette pages.