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Code of Practices

Code of Practice on sewerage and Sanitary Works

(1st Edition - Mar 2000)

 

Part 3 :   Sanitary Works

3.1      Sanitary Drainage System

3.2      Sanitary Plumbing System

3.3      Sanitary Appliances and Fittings

3.4      Standard Drawings for Sanitary Works

Note:

(1) Numerals in parenthesis in this Code of Practice refer to the corresponding drawings.

(2) All text shall be read in conjunction with drawings that provide guidelines for recommended practices.

3.1

Sanitary Drainage System
3.1.1

Objective

 

The system shall convey only wastewater from within the premises to the sewerage system. Rainwater shall not be discharged into sanitary drainage system.

3.1.2

Design Criteria

 

(a)

 

The system shall convey only wastewater from within the premises to the sewerage system. Rainwater shall not be discharged into sanitary drainage system.

(b)

 

The size, length and material shall be chosen to facilitate maintenance and reliable service.

(c)

 

Bends or kinks are to be avoided in any branch/main drain-line.

(d)

 

The branch/main drain-line shall be of the same diameter and laid using the same material throughout its entire length.

(e)

 

The branch/main drain-line shall have a constant gradient. The size and gradient of the drain-line shall be chosen to provide adequate carrying capacity and also allow for adequate ventilation.

(f)

 

In addition, the choice of gradient for the branch/main drain-line shall be such as to maintain self-cleansing velocity (0.9 m/sec) and not to exceed scouring velocity (2.4 m/sec) under normal discharge condition.

(g)

 

The drain-line laid shall be watertight and subjected to a water test under a static head of not less than 1.5 metre of water at the upstream end of the line. The water test shall be done after pipe laying and before placing concrete for haunching or encasing. (Addendum No. 1 - Feb 2001)

(h)

 

Main drain-lines shall not be sited within road reserve and drainage reserve.

(i)

 

A floor trap shall be provided to receive connection from waste appliances before discharging into the branch drain-line. The trap shall have a minimum water seal of 50mm for exclusion of foul air from the sanitary drainage system.

(j)

 

As required by NEA, adequate measures, such as installation of anti- mosquito devices at the floor trap, shall be taken to prevent mosquitoes from breeding in the water seal of the floor trap.

(k)

 

Food shops shall be provided with grease trap/interceptor of adequate capacity so as to prevent discharge of oils, fats and grease directly into the sewerage system. The grease traps shall be maintained such that the effluent from the grease traps shall meet the standards for discharging into the sewerage system

(l)

 

For commercial/shopping complex, separate grease waste discharge pipe connected to a separate discharge stack for future connection to grease trap shall be provided in advance to serve commercial units which are expected to be used as food shops. In addition, sufficient space shall be allocated for siting the grease traps which are to be provided in future to serve the future food shops.

(m)

 

No uPVC pipe shall be used for sewer connection. The connecting drain-line from last inspection chamber to an existing/new manhole shall not be smaller than 200mm in diameter. This is regardless of the size of the existing sewer.

(n)

 

For drain-line connection from the last inspection chamber to an existing 150mm diameter sewer via raised junction or 'Y' junction, it shall follow the size of the existing 150mm diameter sewer.

(o)

 

The drainage system serving the following areas shall be connected to surface storm-water drains.

(i)

 

Common corridors/common verandahs

(ii)

 

Covered areas (void deck except wash area)

(iii)

 

Covered play areas

(iv)

 

Multi-storey car parks (except car washing areas)

(v)

 

Open areas in backyards/courtyards/airwells and other uncovered paved areas within premises where rainwater flows are expected

(vi)

 

Pump islands at petrol stations

(vii)

 

Footbaths, open shower points in public and private swimming pools

3.1.3 

Acceptable Design/ Practices

3.1.3.1 

Branch Drain-line (3-1a) (3-2)&(3-3)

 

(a)

 

The branch drain-line shall have a minimum diameter of 100mm. The length shall preferably not exceed 10 metres.

(b)

 

Where the depth of branch drain-line to an inspection chamber exceeds 1.5 metres the provision of backdrop/ tumbling bay is recommended and the minimum diameter of the branch drain-line shall be 150mm.

(c)

 

The branch drain-line shall be connected obliquely in the same direction of flow as the main drain-line within an inspection chamber. The invert of the branch drain-line at the inspection chamber shall be above the horizontal diameter of the main channel.

3.1.3.2

Main Drain-line (3-1a)

 

(a)

 

The main drain-line shall have a minimum diameter of 150mm and distance between inspection chambers shall not exceed 50 metres.

(b)

 

Inspection chambers shall be provided at all bends, junctions, at changes to the direction of flow or gradient and at changes in pipe diameter or materials.

(c)

 

Where there is any significant difference in invert levels between incoming drain-line and the inspection chamber, a backdrop (3-4) or tumbling bay (3-4) connection shall be made at the inspection chamber.

3.1.3.3

Drain-line under Building (3-5)

 

(a)

 

Every sanitary drain-line shall be laid outside buildings wherever practicable.

(b)

 

Where a drain-line passes under a building, it shall be of heavy duty material (e.g. Ductile iron pipes) and laid in a straight run for the whole distance and shall be encased in concrete of adequate thickness (3-5).

(c)

 

If the drain-line has to pass through a basement wall or laid within basement slab, it shall be of heavy-duty material (e.g. ductile iron pipes). Provision in the design shall be made to take care of differential settlement, to reduce the risk of shear fracture, to ensure water tightness and reliable service.

3.1.3.4 

Drain-line under Driveway and Car park (3-5)

 

(a)

 

The drain-line under driveway and car park shall be of heavy-duty material (e.g. Ductile iron pipes) and appropriately designed to withstand vehicular loading. (e.g. concrete encasement can be provided for the pipes to increase its strength).

3.1.3.5

Bedding, Haunching and Backfilling to Drain-line (3-5)&(3-7a)

 

(a)

 

The design of bedding and haunching for drain-lines depends on the diameter of the pipe, the depth at which it is laid, the trench width, the traffic or other super-imposed loading and the prevailing site conditions. The bedding and haunching increase the drain-line ability to carry the loading. On soft or yielding ground, piling has to be designed. The bedding details are shown in Drawing No 3-5.

3.1.3.6

Inspection Chamber and Ventilation (3-7a)

 

(a)

 

Inspection chamber shall be of brickwall or reinforced concrete construction and be watertight. It shall also be designed to minimise the risk of blockage, facilitate maintenance and prevent flotation in ground where the water table is high. It shall have adequate depth to allow ease of maintenance.

(b)

 

The first inspection chamber shall be ventilated except when there is a discharge/ventilating stack of not less than 100mm diameter or where provision of the ventilation stack would cause odour nuisance to the surroundings.

(c)

 

Details of construction of inspection chamber are shown in Drawing No 3-7a. Where the inspection chamber exceeds 2.5 metres deep, it has to be specially designed. Heavy-duty cast iron frame and cover shall be used in every drive-way and car park.

(d)

 

At the inspection chamber, branch drain-line shall be connected to the main drain-line at a level above the invert level and not less than half the diameter of the main drain-line to ensure smooth flow.

(e)

 

Measures shall be taken to protect the inspection chamber sited within 2.5 m of the top or bottom of an embankment where its slope is steeper than 1:1.5 (e.g. retaining wall).

(f)

 

The last inspection chamber shall be located within 2.5 metres of the lot boundary.

(g)

 

For food shop, no inspection chamber shall be sited within the areas where food is prepared, cooked, stored or served; or other areas where they are likely to give rise to nuisance, health or hygiene hazards during maintenance.

3.1.3.7

Floor Trap at Ground /First Storey Level (3-6)

 

(a)

 

The minimum internal diameter of the outlet of the floor trap at ground/first storey level connecting directly to an inspection chamber shall be 100mm.

(b)

 

The waste pipe shall be connected to a floor trap at the riser below grating and above the water seal of the trap.

(c)

 

Where the floor trap is intended to receive sullage water, it shall be located within covered areas and not subject to surface water runoffs from rain. The floor trap shall be fixed with a frame and grating slightly below the paved floor.

(d)

 

Where a floor trap is sited in a location likely to receive rainwater or on unpaved ground, it shall be fixed with a frame and an unperforated cover.

(e)

 

The maximum depth for a floor trap shall not exceed 600mm to facilitate maintenance. A sump may have to be provided for deeper floor trap.

3.1.3.8

Wash Area (3-8)

 

The wash area shall be constructed under a roof and appropriately kerbed and designed so that no rainwater can enter the sewer. It shall be provided with either a floor waste connecting to floor trap or a floor trap connecting directly to an inspection chamber. The details are shown in Drawing No 3-8.

3.1.3.9

Provisions for Sullage Water Discharge (3-6)(3-10a)& (3-11a)

 
(a)

Sullage water discharge is required to be connected to sewerage system. The specific requirements for sullage water discharge are as follows:

Connection via Floor Trap(3-6)

(i)

 

Backwash from swimming pool filter

(ii)

 

Boiler blowdown via cooling pit

(iii)

 

Covered wash area/service yard within building

(iv)

 

Steam condensate via cooling pit

(v)

 

Waste water from cooling tower

Connection via Cast Iron Gully Trap with Strainer     (Standard Drawing No. PUB/WRN/STD/044)

(vi)

 

Bin centre(3-11a)

(vii)

 

Refuse chute(3-11a)

Connection via Cast Iron Garage Gully Trap with Strainer (Standard Drawing No. PUB/WRN/STD/043)

(viii)

 

Basement car park

(1)  For Basement car park which is not exposed to rain, the drainage system for the car-parking areas may be connected to sewerage system. In such case, adequate numbers of floor waste shall be provided to convey wastewater into the sewerage system so as to prevent flooding or stagnation of water. A cast iron gully trap (Standard Drawing No. PUB/WRN/STD/043) shall be provided before connection to the inspection chamber. At the entrance/exit to the basement car park, minimum crest level shall be provided to prevent any ingress of rainwater.

(2)   For Basement car park which is partially exposed to rain or the car-parking areas are likely to subject to surface water runoffs from rain, the drainage system serving the car parking areas (except car washing areas) shall be connected to surface storm-water drain via an oil interceptor if necessary. In such case, no floor wastes are required. The water discharging into the open drain shall meet the discharge standards as specified by NEA.

Connection via Petrol and Oil Interceptor                                       (Standard Drawing No. PUB/WRN/STD/042)

(ix)

 

Lubrication bay and car washing bay of petrol station

(x)

 

Motor garage

 

(b)

Waste sumps may be provided at multiple junctions of the waste discharge pipes to facilitate ease of maintenance. Details of waste sump are shown in Drawing No 3-10a.

3.1.3.10

Provision of Grease Trap for Food Shop (3-9b)

 

(a)

 

The grease trap shall be sited at locations to facilitate maintenance and will not give rise to nuisances, health hazards and hygiene problems during its operation and maintenance. It shall not be sited within areas where food is prepared, cooked, served or stored.

(b)

 

Standard circular grease traps (Standard Drawings No PUB/WRN/STD/040 and PUB/WRN/STD/041) shall be provided.

(c)

 

Portable grease interceptor may be used where the provision of standard grease traps is not feasible. The portable grease interceptor is allowed to be installed within the individual food shops provided that it must be of a suitable design to allow for easy removal for maintenance.

(d)

 

All portable grease interceptors shall incorporate a mechanical oil-skimming device for automatic removal of free-floating grease and oil to a separate grease/ oil container.

(e)

 

Sufficient floor waste/floor trap shall be provided for the discharge of the sullage water from the kitchen into the grease trap.

3.1.3.11

Sanitary Drainage System for Market (3-12a)

 

(a)

 

Specially designed floor sump (3-13) shall be provided to collect the sullage water from the scupper drains within the stalls and at the service corridors and the common passageways. The details are shown in Drawing No. 3- 12a.

(b)

 

Waste sump (3-10a) shall be sited at service corridors and away from the main public areas. Inspection chamber shall be sited outside the market proper.

3.1.3.12

Sanitary Drainage System for Shower/Bathroom Compartment/ Wash Area at Beach Site/Construction Site/Other area where silt discharge is expected (3-14)

 

(a)

 

Sullage water from shower/bathroom compartment/wash area shall be discharged into a silt trap before connection to an inspection chamber. This is to prevent the sand/silt from entering the sewerage system.

(b)

 

Temporary septic tank is not allowed to serve the temporary work site facilities for developments located in sewered areas and within the water and urban river catchment areas. In such cases, temporary sewer connection to existing sewer is to be provided.

(c)

 

If sewer is not available and the development is located within the water and urban river catchment areas, Developer will have to bring forward the extension of public sewer to serve the construction site. During the interim, temporary holding tanks (i.e. no discharge to sewer/drain) of sufficient capacity (design flow is 200 litres per person per day and minimum capacity is 2000 litres) for sullage water and portable chemical toilets are to be provided. Licensed Waste Contractor shall empty the temporary holding tanks/chemical toilets regularly.

3.1.3.13

Sewer Connection (3-4)

 

The connection from the last inspection chamber to the sewer/manhole shall be constructed in accordance with the Department's Standard Drawing PUB/WRN/STD/007A.

3.1.4

Material and Component (Addendum No. 1 - Feb 2001)

(a)

Pipes and Pipe Fittings

(i)

uPVC                                -   SS 272 : 1983

(ii)

Ductile iron                        -   BS EN 598 : 1995

(iii)

Heavy duty cast iron           -  BS 4622 : 1970

(iv)

Vitrified clay                       -   BS EN 295 : 1991

(v)

Reinforced concrete           -  SS 183 : 1978

(b)

Manhole / Inspection chamber frames and covers                           -   SS 30 : 1999

3.2

Sanitary Plumbing System

3.2.1

Objectives

 

The sanitary plumbing system for any premises shall be designed, installed and maintained so as to carry away wastewater from the building into the sewerage system quickly without creating any nuisance or risk of injury to health.

3.2.2

Design Criteria

 

(a)

 

No sanitary plumbing system shall be used to convey rainwater.

(b)

 

The sanitary plumbing system shall comprise the minimum pipework and be designed to provide adequate capacity to cater for the discharge from the sanitary appliances to which it is connected.

[Reference may be made to the British Standard (BS 5572), U.S - National Standard Plumbing Code or other acceptable standards for the sizing of pipework to provide reliable service. However, the minimum sizes for discharge stacks/ pipes and ventilating stacks/ pipes to be provided shall be in accordance with the requirements laid down in this Code]

(c)

 

The sanitary plumbing system shall be designed to exclude foul air from the discharge pipes or stacks from entering the buildings. In this connection, water seals of sufficient depth (not less than 50 mm) are required to be provided at sanitary appliances and floor traps. The system shall be designed and installed to avoid water seal loss in trap arising from pressure fluctuations through the provision of ventilating pipes/stacks or adequate sizing of discharge stacks as appropriate, for the sanitary plumbing system.

(d)

 

In the case of residential buildings where the sanitary appliances are closely grouped around a discharge stack, the "single stack system" may be adopted for buildings up to six storeys high and the "ventilated stack system" for buildings up to thirty storeys high.

(e)

 

In the design and installation of the sanitary plumbing system, attention shall be given to the need to facilitate access for maintenance and repairs. Access cover and/or cleaning eyes shall be appropriately positioned to enable cleaning, clearing of chokages and inspection to be carried out.

(f)

 

The discharge pipe shall not be located in places where it can cause health and safety hazards such as locating the discharge pipe above any potable water storage tank and electrical transformer/ switchgear.

(g)

 

The discharge pipe shall also not be located in places where it can give rise to nuisance conditions during maintenance. In particular, for buildings under the Land Titles (Strata) Act, discharge pipes shall not run above bedrooms, living room, dining room or kitchen areas of the strata unit below. Where such routing cannot be avoided, suitably designed service duct to allow access for maintenance shall be provided.

(h)

 

As required by NEA, adequate measures, such as installation of anti-mosquito devices at the floor trap, shall be taken to prevent mosquito from breeding in the water seal of the floor trap.

(i)

 

For sewage collected below ground level, sewage ejector, solids divertor or other appropriate pumping installation will have to be provided.

(j)

 

The sanitary plumbing system shall be tested for water and air tightness either by means of an air test, smoke test or water test for soundness of the installation. Reference can be made to BS 5572 for details.

3.2.3

Acceptable Design / Practice

3.2.3.1

Fully Ventilated Sanitary Plumbing System (3-15a)&(3-16a)

 

(a)

 

The fully ventilated system is used where there are large numbers of sanitary appliances in range or where they have to be widely dispersed.

(b)

 

In the fully ventilated system, separate discharge and ventilating stacks have to be provided and be extended to the atmosphere. Individual traps/soil sanitary appliances connected directly to the discharge pipe or stack need to be provided with branch ventilating pipe which is connected to ventilating stack.

(c)

 

The discharge stack shall have a uniform diameter of not less than 100mm throughout its entire length.

(d)

 

The trap connecting directly to a discharge pipe shall be provided with a branch ventilating pipe of not less than 50mm in diameter.

(e)

 

The ventilating pipe shall be constructed upwards individually and be connected to a main ventilating stack. Such connection shall be above the spill over level of the soil sanitary appliance or floor trap served by such ventilating pipe. The details are shown in Drawings No. 3-19 & 3-20.

(f)

 

The top end of every ventilating stack shall either terminate as high as the discharge stack or connect into the discharge stack at a point not less than 150mm above the spill over level of the topmost soil sanitary appliance or floor trap.

(g)

 

For multi-storey buildings of seven-storey or higher (3-16a), the discharge pipe serving the second storey shall be connected to a secondary discharge stack of diameter not less than 100mm. This stack shall be extended to serve as ventilating stack but may be reduced to 75mm diameter.

(h)

 

Cross venting between the ventilating stack and the discharge stack shall be provided at every ten storeys.

3.2.3.2

Single Stack Sanitary Plumbing System (3-17b)

 

(a)

 

The single stack system may be used for buildings up to six storeys high where there are single appliances connected to a discharge stack or where the sanitary appliances/ fittings are closely grouped round a discharge stack which is large enough to limit pressure fluctuations without the need for a ventilating stack.

(b)

 

The main discharge stack shall have a uniform diameter of not less than 150mm without offset throughout its entire length. However, for conventional housing, a main discharge stack of 100mm diameter may be provided.

(c)

 

The length of the discharge pipe connecting to the discharge stack shall not be more than 2.5m and there shall be not more than two connections made to the discharge pipe.

3.2.3.3

Ventilated Stack Sanitary Plumbing System (3-18b)

 

(a)

 

The ventilated stack system may be adopted in situations where there are close groupings of sanitary appliances around the discharge stack in buildings up to thirty storeys high.

(b)

 

The main discharge stack shall have a uniform diameter of not less than 150mm throughout its entire length.

(c)

 

Separates discharge stack (secondary discharge stack) of diameter not less than 100mm shall be provided to serve the second and third storeys. This secondary discharge stack shall be extended to serve as ventilating stack.

(d)

 

Cross venting between the ventilating stack and the discharge stack shall be provided at third, sixth, ninth, twelfth, fifteenth, eighteenth, twenty-first, twenty-fourth and twenty-seventh storeys.

(e)

 

The length of a discharge pipe connecting to the discharge stack shall not be more than 2.5m and there shall be not more than two connections made to the discharge pipe.

3.2.3.4

Discharge Pipe/Stack, Ventilating Pipe/Stack for Sanitary Plumbing System (3-15a) to (3-21)

Unless otherwise indicated, the following clauses are applicable to all the above 3 types of sanitary plumbing systems:

 

(a)

 

The discharge pipe shall have a minimum size of 100mm and be made of the same material throughout its entire length. The pipe shall not be reduced in diameter in the direction of flow.

(b)

 

In the case of the "fully ventilated system" and "ventilated stack system", the discharge stack shall, as far as practicable, not form any offset throughout its entire length. Where offset is to be made, large radius bends of at least 200mm radius shall be used and cross venting between the ventilating stack and the discharge stack is required above and below the offset (3-21).

(c)

 

Swept branch connections from discharge pipe to discharge stack are recommended. Directly opposite discharge pipes without swept entries shall be at least 200mm vertically apart so that discharge from one branch into the other is avoided.

(d)

 

The discharge pipe and discharge stack shall be securely supported or fixed to the wall or roof slab of the building.

(e)

 

The discharge pipe and discharge stack shall be easily accessible. Access covers for cleaning eyes shall be positioned to allow cleaning and maintenance equipment to be easily inserted into the pipework and to permit cleaning or clearing of all parts of the system. Access cover on the invert of pipe shall be avoided. Access for rodding and testing shall be provided at or near the foot of the discharge stack and at junctions of discharge pipe/stack.

(f)

 

The ventilating pipe shall be fixed as close to the crown of the trap as practicable. Other aspect of the construction of ventilating stack, cross venting, termination of discharge stack and ventilating stack are shown in Drawing No. 3- 15a, 3-16a, 3-17b, 3-18b & 3-21.

(g)

 

The ventilation stack shall not be terminated in any private premises or private roof area that is designed for use by the occupants. To avoid termination of ventilation stack in private premises or roof areas, the ventilating stack may be offset or connected to a common pipe of adequate size and extended for termination in the open air at the highest point of the building or other suitable location that will not cause smell nuisance or health hazard to the occupants. The recommended height of the ventilating stack above roof is shown in Drawing Nos. 3-15a, 3-16a, 3-17b & 3-18b. (Addendum No.1-Feb 2001)

3.2.3.5

Connection of Discharge Stack to Branch Drain-line (3-22)

 

(a)

 

The discharge stack shall be connected directly to the inspection chamber. Where individual connections of discharge stacks are impracticable, a common pipe of adequate size to serve the discharge stacks may be provided to suit connection to a branch drain-line.

(b)

 

In the case of multi-storey buildings of 7-storey or higher, both discharge and ventilating stacks are to be connected to inspection chamber. The invert of the discharge end of the ventilating stack shall be at least one diameter above that of the discharge stack.

3.2.3.6

Access to Pipework Enclosure

 

(a)

 

No pipe other than the ventilating pipe or ventilating stack and waste pipe shall be encased in columns, beams, walls, or floor slabs.

(b)

 

Discharge pipes or stacks may be accommodated in enclosures such as ducts which shall be of suitable size and provide ready access openings for maintenance and testing.

(c)

 

Access openings shall preferably be provided to joints or junctions of discharge pipes/stacks and other fittings that may require maintenance.

3.2.4

Material and Component (Addendum No. 1 - Feb 2001)

The following materials that comply with the stipulated standards are acceptable for use in sanitary plumbing system viz:

(i)

uPVC                               -   SS 213 : 1998

(ii)

Ductile iron                       -   BS EN 598 : 1995

(iii)

Hubless cast iron               -   CISPI : 301 : 1995

                                       -   CISPI : 310 : 1995

                                       -   BS 6087 : 1990

                                       -   ASTM C 564 : 1995

(iv)

Spigot/Socket cast iron       -  SS 33 : 1975

3.3

Sanitary Appliances and Fittings

3.3.1

Objectives

Sanitary wares, sanitary pipes and fittings are part of the sanitary plumbing and drainage system for the conveyance of wastewater from within the premises to the sewerage system. Its design and construction have a great impact on the proper functioning of the sanitary plumbing system. The proper selection and installation of sanitary wares, pipes and fittings will reduce the risk of danger to health arising from blockage, leakage or surcharge.

3.3.2

Selection/ Design Criteria

 

(a)

 

The sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers used in the sanitary plumbing and drainage system shall be of a type, size, quality and workmanship as specified in the Code and shall comply with the Standards prescribed in this Code of Practice. (Addendum No.1-Feb 2001)

(b)

 

Sanitary appliances shall be secured in position and installed in a manner that facilitate disconnection to the sanitary piping when required. The supports and brackets used for fixing of the sanitary appliances to wall shall be of adequate strength to withstand the fully loaded weight of the appliance. In no circumstances should any pipework be relied upon for support or fixing the appliance. 

(c)

 

Connection of Soil Sanitary Appliance

(i)

 

Soil Sanitary Appliance is for the reception and discharge of excretory matter. Examples of soil sanitary appliances are water closet pan, urinal and bidet etc.

(ii)

 

Direct connection from any water service pipe shall not be made to any part of a soil sanitary appliance other than a connection through the flushing cistern or flush valve as detailed under Clauses 3.3.3.2 and 3.3.3.4 of this Section respectively. This is to prevent contamination of the potable water system.

(iii)

 

The soil sanitary appliance shall have at least one trap with a water seal of not less than 50 mm before connecting directly to a separate branch drain-line to an inspection chamber on first storey level or to a discharge pipe on upper storey level.

(d)

 

Connection of Waste Sanitary Appliance

(i)

 

A waste sanitary appliance is for the reception and discharge of water for ablutionary, cleaning or culinary purpose. Examples of waste sanitary appliances are sink, basin, bath and shower tray etc.

(ii)

 

The waste sanitary appliance shall be provided with a waste fitting trap for connection to the waste pipe.

(iii)

 

Waste pipes serving waste sanitary appliances are to be adequately sized to handle the anticipated flow. The waste pipe shall connect above the water seal of the floor trap.

(iv)

 

The waste sanitary appliance which is suspended shall be fixed to the wall by means of brackets which are built or screwed into the wall. All installation screws shall be corrosion resistant.

(v)

 

Loop venting (3-24) is required where a group of 3 or more wash basins are connected in series. However, the loop venting shall be terminated separately to the atmosphere. The minimum diameter of loop venting pipe shall be 25 mm. Alternatively, Air Admittance Valve may be used.

3.3.3

Acceptable Practices on Installation of Sanitary Appliances

3.3.3.1 

Water Closet Pan

 

(a)

 

General

(i)

 

The water closet pan shall be of a design suitable for use with low capacity flushing cistern or flush valve and shall conform to the functional requirements and tests in the relevant Singapore Standard SS 379 (1996).

[Note: Under the Public Utilities (Water Supply) Regulations, a flushing device for a water closet shall deliver not more than 4.5 litres of water per flush]

(ii)

 

The water closet pan shall be securely installed by an approved method of fixing (3-23). The details are shown in Drawing No. 3- 23.

 

(b)

 

Oriental Water Closet Pan (Squatting Type)

(i)

 

The oriental water closet pan installed in a combined bath and water closet compartment shall be fixed at least 75mm above floor level.

(ii)

  The oriental water closet pan shall be installed within a specially designed recessed reinforced concrete floor slab such that no part of the pan shall protrude below the floor slab. The pan shall then be bedded in sand and concrete over to provide an impervious surround. The floor surrounding the pan shall also be graded to drain off any water into the pan (3-26)
 

(c)

 

Pedestal Water Closet Pan (3-23)

The jointing of the outlet of the water closet pan to the branch drain-line or discharge pipe shall be done either with a purpose made flexible connector (pan collar or floor flange) or other approved method of jointing.

 

(d)

 

Wall Hung Water Closet Pan

Wall hung water closet pan shall be fixed with stainless steel bolts and nuts or other approved means to an independent support frame such that no strain is transmitted to the water closet pan connector or any other part of the plumbing system. The support frame, depending on the design, should be securely fixed within the structure of the building.

3.3.3.2

Flushing Cistern

 

(a)

 

The flushing cistern serving a water closet pan shall be of the low capacity type and shall conform to the specifications, tests and installation requirements in the relevant Singapore Standard SS 378 (1996)

[Note: Under the Public Utilities (Water Supply) Regulations, a flushing device for a water closet shall deliver not more than 4.5 litres of water per flush.]

(b)

 

The flushing cistern, except when it is of a self supporting close-coupled water closet suite, shall be installed abutting and firmly fixed to the wall by either stainless steel bolts and nuts, stainless steel brackets (or support pads) or other approved means.

(c)

 

The connection of the flush pipe of the flushing cistern to the water closet pan and the urinal shall be made using a purpose made connector or bush to ensure a robust and watertight joint.

(d)

 

The high level flushing cistern shall be fixed to an oriental water closet pan with a flush pipe of height not less than 1.5 metres between the bottom of the cistern and the top of the water closet pan. The flush pipe shall not be less than 32 mm in diameter.

(e)

 

For low level flushing cistern the minimum internal diameter of the flush pipe shall be 35 mm.

3.3.3.3

Urinal (3-25)

 

(a)

 

The urinal shall be of the individual stall or wall hung units. The urinal shall be more than 300 mm wide and the collection area shall project from the wall by at least 300 mm.

(b)

 

The individual urinal shall be firmly fixed to the wall by either stainless steel bolts and nuts or other approved means. There shall be a minimum of three support points for wall hung urinal to provide support for uneven loading or side loading situations.

(c)

 

The urinal shall be provided with a fitting trap of at least 40mm in diameter. The connection (by means of a urinal trap of at least 75 mm in diameter) shall be made directly to an individual branch drain-line to an inspection chamber on first storey or to a discharge pipe on upper storey level.

(d)

 

A urinal trap shall be provided to serve a maximum of 10 urinals. For more than 10 urinals, more than one trap shall be provided.

(e)

 

Where a group of urinals are connected in series, loop venting is required (see Drawing No 3-25). Alternatively, Air Admittance Valve may be used.

(f)

 

The flush pipe for urinal flush valve shall be made of either stainless steel or chrome-plated copper alloy and shall preferably be concealed.

3.3.3.4

Flush Valve

 

(a)

 

The flush valve shall conform to the requirements in the SS CP 48 - Code of Practice for Water Services.

[Note: Under the Public Utilities (Water Supply) Regulations, (1) A flush valve for a water closet shall deliver not more than 4.5 litres of water per flush and a flush valve for urinal shall deliver not less than 1.5 litres and not more 2.5 litres of water for individual urinal unit; (2) Flush valve shall not be used in residential premises.]

(b)

 

Only water closets and urinals in non-domestic buildings/premises may be fitted with flush valves.

(c)

 

The flush valve shall be preferably activated by depressing a push-knob. All adjusting mechanisms shall be temper proof and securely concealed. Flush valve with only the activating knob exposed to the user is preferred.

(d)

 

The flush pipe shall be made of either stainless steel or chrome-plated copper alloy and preferably concealed.

(e)

 

The connection of the flush pipe of the flush valve to the water closet pan and urinal shall be made using a purpose made connector to ensure a robust and watertight joint.

3.3.3.5

Automatic Flushing Devices

 

(a)

 

As required by NEA, all water closets and urinals in public toilets shall be fixed with sensor flush valves.

(b)

 

All automatic flushing devices shall be activated by sensors. Automatic flushing devices that can be used are either:

(i)

 

Sensor devices/mechanisms that can activate an approved manual flush valve; or

(ii)

 

A fully integral sensor-operated flush valve.

3.3.3.6

Bidet

 

(a)

 

The bidet shall be provided with a spray nozzle fixed above the spill over level of the bidet pan and shall conform to the requirements in the SS CP 48 - Code of Practice for Water Services.

(b)

 

Water for the flushing of the bidet shall not be supplied directly from the water supply unless through an approved vacuum breaker and check valve or other approved means for preventing backflow or back-siphonage and controlled by approved stop-valve.

(c)

 

The bidet shall be provided with a fitting trap of at least 40 mm in diameter. The connection by means of a bidet trap of at least 75 mm in diameter shall be made to an inspection chamber on first storey level or to a discharge pipe on upper storey level (3-25).

(d)

 

The bidet shall be installed in accordance with the pedestal water closet pan or the wall hung water closet pan as specified in Clause 3.3.3.1(c) or 3.3.3.1(d).

3.3.3.7

Special Sanitary Appliance (Addendum No. 1 - Feb 2001)

Approval of PUB should be obtained for the use of any special sanitary appliance not covered under this Section. This includes the special soil sanitary appliances for hospital.

3.3.3.8

Bath and Shower Unit

 

(a)

 

The supports for the bath/shower unit shall be of sufficient strength to obviate strain on any pipework connection.

(b)

 

The joints between the edge of the bath/shower unit and the wall shall be watertight.

(c)

 

Where a dwarf wall is to be erected to support the bath, an access opening is to be provided in the wall to facilitate maintenance of the waste pipe under the bath.

3.3.3.9

Floor Trap (3-6)& (3- 8)

 

(a)

 

The waste pipe shall be connected above the water seal of the floor trap and shall be as short as possible.

(b)

 

The minimum internal diameter of the outlet of the floortrap shall be 75mm.

(c)

 

The trap with an outlet of 75mm in diameter shall have a water seal of not less than 75mm.

(d)

 

The floor trap at upper storey level shall be connected to a discharge pipe.

(e)

 

The riser to the floor trap shall be of the same diameter as the opening of the trap.

(f)

 

Adequate number of floor traps shall be provided for bathroom or shower compartment. The floor trap shall be positioned as near to the tap point/shower point as possible and the floor appropriately graded/designed so as to enable quick drainage of the wastewater from tap points or shower points to the floor traps to avoid wetting of the whole toilet floor area.

g)

 

For group showers, a floor trap shall be provided to serve a maximum of 5 showers. A floor waste or channel of adequate capacity shall be provided in the shower compartments to convey the sullage water to the floor trap.

3.3.3.10

Floor Waste

 

(a)

 

Floor waste shall be connected to a floor trap above the water seal of the trap and the length of the waste pipe between the floor waste and floor trap shall be as short as possible.

(b)

 

The minimum internal diameter of the floor waste shall be 50mm. However, where the floor waste also serve a waste sanitary appliance, the minimum internal diameter shall be 75 mm.

(c)

 

The floor waste shall be covered with a grating.

3.3.3.11

Grating and Cover for Floor Trap and Floor Waste

 

(a)

 

The grating and cover shall be constructed of suitable approved material like durable plastic and stainless steel.

(b)

 

The grating and cover shall be of an approved design so as to enable them to be secured to deter the unwarranted opening of the grating or cover and hence introduction of garbage or other solid waste into the sewerage system.

3.3.4 

Shallow Floor trap for Prefabricated Toilet Unit

Approval of PUB shall be obtained for the use of shallow floor traps for Prefabricated Toilet Unit.

3.3.5

Material and Component (Addendum No. 1 - Feb 2001)

 

(a)

 

Sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers that comply with the Singapore Standards or other Standards as prescribed in this code and certified by a conformance assessment body or certification body accredited to the relevant authority (SAC-SINGLAS) or bodies under its Mutual Recognition Agreements (MRAs) are acceptable for use in sanitary work/sewerage works. Separate approval from PUB for their use is not required. The Department may require such certificates/test reports to be submitted for verification.

(b)

 

Sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers for use in sanitary works/sewerage works may be listed in the "Product Listing Scheme" (PLS) administered by the PSB Corporation Pte Ltd. The PLS directory of approved products is obtainable from PSB at 1 Science Park Drive or can be downloaded from PSB Website at URL Address:
http://www.psbcorp.com/productlisting.aspx 

(c)

 

Approval of the Department shall be obtained for the use of other types/designs of sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers not specified in this Code. These sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers must comply with the Singapore Standards or other acceptable Standards if no Singapore Standard is available.

(d)

 

All sanitary wares, pipes and fittings, manhole/ inspection chamber frames and covers shall be legibly marked with the manufacturer's name/brand name or mark and the standards under which the product conform to. The markings may be cast-on, cold stamped or painted on the product. Alternatively, labels may be affixed or attached to the product.

3.4

Standard Drawings for Sanitary Works

 
Last updated on 29 Sep 2011