SECTION 7
Schedule 2: Paragraph 16: Cold water services
- (1) Every pipe supplying water connected to a storage cistern shall be fitted with an effective adjustable valve capable of shutting off the inflow of water at a suitable level below the overflowing level of the cistern.
(2) Every inlet to a storage cistern, combined feed and ex[pansion cistern, WC flushing cistern or urinal flushing cistern shall be fitted with a servicing valve on the inlet pipe adjacent to the cistern.
(3) Every storage cistern, except one supplying water to the primary circuit of a heating system, shall be fitted with a servicing valve on the outlet pipe.(4) Every storage cistern shall be fitted with-
- an overflow pipe, with a suitable means of warning of an impending overflow, which excludes insects;
- a cover positioned so as to exclude light and insects; and
- thermal insulation to minimize freezing or undue warming.
(5) Every storage cistern shall be so installed as to minimise the risk of contamination of stored water. The cistern shall be of an appropriate size, and the pipe connections to the cistern shall be so positioned, as to allow free circulation and to prevent areas of stagnant water from developing.
Guidance
Float-operated valves
G16.1 Float-operated valves and other fittings for controlling flow to cisterns, including flushing cisterns, should:
- be capable of controlling the flow of water into any cistern or apparatus and, when closed, be watertight and remain watertight; and,
- incorporate, as applicable, a renewable seat and a washer which are resistant to both corrosion and erosion by water, or have some other no less effective valve closure assembly; and,
- as applicable, have a float which is constructed of a material capable of withstanding without leaking any water temperature in which it operates or is likely to operate, and has a lifting effort such that when not more than half immersed, the valve is capable of drop-tight closure against the maximum operating pressure at that elevation in the building; and,
- when acting via an operating lever, and when the valve is closed, will withstand without bending or distorting a force twice that to which it is ordinarily subject and, in the case of a G 1/2 size valve, is constructed so that the water shut-off level may be altered or adjusted without bending the float lever; and,
- where used in cisterns storing water other than for drinking purposes, the installation of the fitting should be such that it is capable of satisfying backflow prevention requirements when the water level in the cistern is level with the centreline of the float-operated valve.
G16.2 The requirements for float-operated valves may be satisfied as follows:
- for use in WC cisterns - should comply with BS 1212. Parts 2, 3 or 4; and,
- for use elsewhere - should comply with BS 1212: Part 1, 2, 3 or 4.
G16.3 Float-operated valves which are subject to hot water at the inlet should conform to clause G16.1 and be constructed of materials capable of withstanding without leaking any ordinary operating water temperature to which they are likely to be subjected. So far as is reasonably practicable, their operation should not be prevented or impaired by scale. Having regard to any scale which is likely to be deposited on the valve or float, the valve should be capable of being adjusted to prevent any flow through the valve above the required water level.
Inlets to cisterns
G16.4 Inlets to all cisterns should be provided with a servicing valve to facilitate maintenance, and a float-operated valve or some other no less effective device which is capable of controlling the flow of water into the cistern. The servicing valve should be fitted as close as reasonably practical to the float operated valve or other device. This does not apply to a pipe connecting two or more cisterns each of which has the same overflowing level.
G16.5 Float-controlled valves or equivalent inlet devices should be securely and rigidly attached to the cistern and installed so that the valve closes when the level of the water is not less than 25 mm below the overflowing level of the cistern. Where the cistern is fitted with an approved alternative to a warning pipe, such as an indicator instrument or a visual or audible alarm, the inlet valve is to close when the water level is not less than 50 mm below the overflowing level of the cistern.
Outlets from cisterns
G16.6 Where practicable all outlets from a cistern should be taken from the bottom of the cistern.
G16.7 Except for cisterns supplying water to primary circuits or heating circuits, all outlets other than vent pipes, overflow pipes, and warning pipes relating to storage cisterns supplying water to cold water taps and secondary hot water systems, should be fitted with a servicing valve as close to the cistern as is reasonably practicable.
Warning and overflow pipes
G16.8 All cisterns, except automatically operated urinal flushing cisterns, should be provided with a warning pipe, or some other no less effective device, installed in such a manner that it discharges immediately the water in a cistern reaches the defined overflowing level. Where an alternative no less effective device is installed instead of a warning pipe, an overflow pipe should also be installed. The outlet end of a warning or overflow pipe is not to be at a higher level than the inlet end; it should be installed on a downward inclined plane, and not comprise, include, or have connected to it, any flexible hose.
G16.9 Warning or overflow pipes from any cistern should not be installed to discharge into any other cistern.
G16.10 A warning/overflow pipe should be not less than 19 mm internal diameter, but the actual internal diameter of the pipe(s) installed should be capable of taking any possible flow in the pipe arising from any failure of the inlet valve.
G16.11 When determining the size of an overflow pipe account should be taken of any insect or vermin screen installed, which may reduce the nominal flow capacity of the overflow pipe.
G16.12 When two or more cisterns have a common warning pipe the pipework should be arranged so that the overflow from any cistern cannot enter another. The location of the cistern overflowing must be readily identifiable and the discharge should be in a conspicuous position.
Cold water storage cisterns
G16.13 Cisterns storing water for domestic purposes should be watertight and, where required, be lined or coated with a suitable impermeable material; they shall be provided with warning and overflow connections, as appropriate, which are so constructed and arranged as to exclude insects. They should have a rigid, close fitting and securely fixed cover which is not airtight but which excludes light and insects from the cistern; be made of a material or materials which do not shatter or fragment when broken and which will not contaminate any water which condenses on its underside; and, in the case of a cistern storing more than 1,000 litres of water, be constructed so that the cistern may be inspected and cleansed without it having to be wholly uncovered. See Figure 7.1.
G16.14 Every cistern should be adequately supported to avoid distortion or damage and only installed in a place or position where the inside may be readily inspected and cleansed, and any float-operated valve or other controls may be readily installed, repaired, renewed or adjusted. The cistern should have a minimum unobstructed space above of not less than 350 mm. See Figure 7.2.
G16.15 Where the required capacity of water is provided by the use of two or more cisterns, the inlets and the outlets of the cisterns should be located so that water passes through the whole of the cisterns and short-circuiting does not occur.
Figure 7.1: Requirements for storage cisterns
Figure 7.2: Minimum clear space required above storage cisterns
Published 22 December 1999
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