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SECTION 4 Schedule 2: Paragraphs 8, 9, 10, 11, 12 and 13: Water system design and installation No water fitting shall be installed in such a position, or pass through such surroundings, that it is likely to cause contamination or damage to the material of the fitting or the contamination of water supplied by the water undertaker. Any pipe supplying cold water for domestic purposes to any tap shall be so installed that, so far as is reasonably practicable, the water is not warmed above 25°C. (1) Every supply pipe or distributing pipe providing water to separate premises shall be fitted with a stop valve conveniently located to enable the supply to those premises to be shut off without shutting off the supply to any other premises. (2) Where a supply pipe or distributing pipe provides water in common to two or more premises, it shall be fitted with a stop valve to which each occupier of those premises has access. Water supply systems shall be capable of being drained down and be fitted with an adequate number of servicing valves and drain taps so as to minimize the discharge of water when water fittings are maintained or replaced. A sufficient number of stop valves shall be installed for isolating parts of the pipework. (1) The water system shall be capable of withstanding an internal water pressure not less than 1½ times the maximum pressure to which the installation or relevant part is designed to be subjected in operation ("the test pressure"). (2) This requirement shall be deemed to be satisfied- in the case of a water system that does not include a pipe made of plastics, where- the whole system is subjected to the test pressure by pumping, after which the test continues for one hour without further pumping; the pressure in the system is maintained for one hour; and there is no visible leakage throughout the test; in any other case, where either of the following tests is satisfied- TEST A the whole system is subjected to the test pressure by pumping for 30 minutes, after which the test continues for 90 minutes without further pumping; the pressure is reduced to one third of the test pressure after 30 minutes; the pressure does not drop below one third of the test pressure over the following 90 minutes; and there is no visible leakage throughout the test. TEST B the whole system is subjected to the test pressure by pumping for 30 minutes, after which the pressure is noted and the test continues for 150 minutes without further pumping; the drop in pressure is less than 0.6 bar (60kPa) after the following 30 minutes, or 0.8 bar (80kPa) after the following 150 minutes; and there is no visible leakage throughout the test. Every water system shall be tested, flushed and where necessary disinfected before it is first used.

Guidance

General

G8.1   The following factors should be taken into consideration in the design of a water supply system:

1. the estimated daily consumption and the maximum and average flows required, together with the estimated peak flow; and,
2. the location of the available supply main and minimum and maximum pressures available; and,
3. the quality, quantity and pressure required at outlets and the available pressures at various times during a typical day; and,
4. the cold water storage capacity required, if any; and,
5. the likelihood of ground subsidence due to mining activities or any other reason if it will have a detrimental effect on the supply; and,
6. the likelihood of existing contamination of the site; and,
7. transient or surge pressures that may arise during the operation of the system.

G8.2   Subject to specific requirements of the local water undertaker, water may be supplied to appliances and draw-off points:

1. from a distributing pipe deriving its supply from a storage cistern; or,
2. directly from and under pressure from a supply pipe; or,
3. a combination of 'a' and 'b' subject to necessary precautions being taken to prevent cross-connections and backflow; or,
4. from a pumped supply or distributing pipe, where this is necessary due to lack of pressure, .

See Figure 4.1 for examples of typical installations of a, b and c in a house.

Design flow rates

G8.3   Generally, installations incorporating cold water systems and hot water storage systems should be designed and installed so that the design flow rates given in Table 4.1, which is based on Table 3 of BS 6700, will be available at each outlet, and any group of outlets where the total demand does not exceed 0.3 litre/second, when only that outlet or group of outlets is discharging. When simultaneous discharge occurs the rate of flow of water at any outlet in use should not be less than the minimum rate shown.

G8.4   Where hot water systems are installed that incorporate instantaneous heaters or combination boilers the rates of flow shown in Table 4.1 may not be achievable and the system should be designed accordingly.

G8.5   Water fittings should not be laid or installed in, on, or pass through any contaminated environment; for example, foul soil, refuse or a refuse chute, ashpit, sewer, drain, cesspool, manhole or inspection chamber.

G8.6   Storage cisterns holding water for domestic purposes and other water fittings are to be installed in such positions that no surface, ground or foul water, or any other water that is unwholesome, may enter the cistern or fitting.

Distribution temperature of cold water

G9.1   So far as is reasonably practical the temperature of water within cold water pipes should not exceed 20⁰ C and adequate measures should be taken to ensure that this temperature is not exceeded..

Operational fittings

G10.1   Operational fittings such as stopvalves, servicing valves and drain taps should be readily accessible for operation and maintenance.

G10.2   Operational fittings may be located in a duct, access chamber or cupboard provided with a hinged door or removable cover which is visible at all times. The door or cover should not be covered with any decorative material, such as carpet, wall or floor tiling or wallpaper, which requires removal to access the door or cover.

Stovalves to premises

G10.3   Every supply and distributing pipe providing water to premises should be fitted with a stopvalve to control the supply to those premises only. See Figure 4.2.

G10.4   Every supply and distributing pipe providing water in common to two or more premises are to be fitted with a stopvalve (whether inside or outside premises) to which each occupier of premises has access. See Figures 4.2band 4.2c.

Location of stopvalve in buildings

G10.5   Stopvalves should, so far as reasonably practical, be installed inside the premises above floor level, near where the supply pipe enters the building and so installed that closure of the stopvalve will prevent the supply of water to all points of use.

Provision of servicing valves

G11.1   Inlets to all float-operated valves, cisterns, clothes washing machines, dishwashing machines, water heaters, water softeners and other similar appliances should be provided with a servicing valve to facilitate maintenance.

G11.2   Servicing valves should be fitted as close as is reasonably practical to float operated valves or other inlet devices of an appliance.

G11.3   Servicing valves may be of the screwdown or spherical type.

Provision of draining taps

G11.4   Sufficient draining taps should be provided to facilitate the draining of all supply and distributing pipes within the building.

G11.5   Draining taps should be of the screwdown type conforming to BS 2879 or, where located in a frost free location, of an approved spherical type.

G11.6   Draining taps should not be buried or covered with soil, or installed so that they are submerged, or likely to be submerged.

Redundant fittings and dead legs

G11.7   Any draw-off fitting that is permanently removed from the installation should have the branch pipe serving the fitting disconnected at its source.

Testing

G12.1   The whole installation should be tested hydraulically on completion by subjecting all supply and distributing pipes, fittings and connections to appliances, to an internal test pressure of 1.5 times the maximum operating pressure for the installation or the relevant part..

G12.2   For systems that do not include any plastics pipes (that is, rigid pipe materials such as copper, stainless steel, etc), the requirement shall be deemed to be satisfied if:

1. the whole of the system is subjected internally to the test pressure by pumping, after which the test continues without further pumping;
2. the pressure in the system does not drop below the test pressure over the next one hour period and there is no visible leakage,

in accordance with Clause 3.1.12.3.3 of BS 6700.

G12.3   For systems that include any plastics pipes, the requirement shall be deemed to be satisfied if, either:

Test A

1. the whole of the system is subjected internally to the test pressure which is maintained by pumping for 30 minutes, after which the test continues without further pumping; and
2. the pressure in the system is carefully reduced to one third of the test pressure; and
3. the pressure does not drop over the following 90 minutes and there is no visible leakage;

or in accordance with Clause 3.1.12.3.4 (Test procedure A) of BS 6700, or

Test B

1. the whole of the system is subjected internally to the test pressure and is maintained by pumping for 30 minutes, after which the pressure is noted and the test is continued without further pumping; and
2. the pressure drop is less than 0.6 bar after a further 30 minutes; and
3. the pressure drop is less than 0.2 bar after the next 120 minutes and there is no visible leakage,

or in accordance with Clause 3.1.12.3.4 (Test procedure B) of BS 6700.

Flushing

G13.1   Flushing of installations should be in accordance with Clause 3.1.10.1 of BS 6700.

Disinfection

G13.2   After testing and flushing, systems should be disinfected in the following instances:

1. new installations (except private dwellings occupied by a single family); or,
2. major extensions or alterations (except private dwellings occupied by a single family); or,
3. underground pipework (except localised repairs or insertion of junctions); or,
4. where it is suspected that contamination may have occurred, e.g. fouling by sewage, drainage, animals or physical entry by site personnel for interior inspection, painting or repairs; or
5. where a system has not been in regular use and not regularly flushed.

Table 4.1: Recommended design flow rates of cold and hot water to sanitary appliances
Outlet fitting or appliance	Rate of flow - litres/second
	Design rate	Min. rate
WC cistern (to fill in 2 minutes)	0.13	0.05
WC pressure flushing valve (DN 20)	1.5	1
WC flushing trough (per WC served)	0.15	0.1
Urinal cistern (each position served)	0.004	0.002
Urinal flushing valve	0.3	0.15
Washbasin (pillar or mixer taps)	0.15	0.1
Handbasin (pillar or mixer taps)	0.1	0.07
Handbasin (spray or spray mixer taps)	0.05	0.03
Bidet	0.2	0.1
Bath (G ¾)	0.3	0.2
Bath (G 1)	0.6	0.4
Shower head	0.2	0.1
Kitchen sink (G ½)	0.2	0.1
Kitchen sink (G ¾)	0.3	0.2
Kitchen sink (G 1)	0.6	0.4
Washing machine	0.2	0.15
Dish-washing machine	0.15	0.1
1. Flow rates required for washing and dish-washing machines for other than single dwellings should be obtained from the manufacturer. 2. Mixer fittings or combination tap assemblies deliver less flow than two separate taps; it is suggested that 70 % of the above flow rates may be sufficient. 3. The rate of flow required to shower heads will depend on the type fitted; the advice of the shower manufacturer should be sought. 4 The above rates of flow to appliances are applicable where hot water centralised storage systems are installed. Where hot water systems incorporate instantaneous heaters or combination boilers the rates of flow shown in the Table may not be achievable and the system should be designed accordingly.

Figure 4.1: Typical examples of water supply systems in houses

Figure 4.2: Examples of location of stopvalves

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Published 22 December 1999

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