Page 292 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Inlet requirements for domestic cisterns

The inlet requirements state that all cisterns will be fitted with an adjustable
water inlet control device. These devices are usually float-operated valves that
must conform to BS 1212. The British Standard defines four
High types of float-operated valve that are suitable for use in cold
pressure
orifice water cisterns:

Water outlet ● Part 1 – Portsmouth type (permitted only with a backflow
prevention device)
● Part 2 – brass diaphragm type
● Part 3 – plastic diaphragm type
Water inlet
● Part 4 – diaphragm equilibrium type (used only on WC
Union
cisterns).
Plunger Diaphragm Figure 5.45 shows a cross-section of a float-operated valve,
washer
which can be made of brass (BS 1212 Part 2) or plastic (BS 1212
Float adjustment screw
Part 3). The adjustment screw allows for the valve to be set at
the correct water level. It is important to note that BS 1212
p Figure 5.45 A BS 1212 Part 2 and 3 float-operated only covers valves up to 54 mm in size. Any float-operated valve
valve with a high-pressure orifice fitted fitted that exceeds this size must be authorised by one of the
following bodies:

● Water Regulations Advisory Service
● Water Fittings and Materials Directory
● your local water authority.

A low-pressure orifice, generally coloured red, would be used if the supply
pressure was low or the float-operated valve was being fed from another
cistern, say, on an indirect cold water system to a WC. The difference between
p Figure 5.46 A BS 1212 Part 2
float-operated valve an HP and LP orifice is simply that the LP orifice has a wider opening to allow
greater flow of water.

Water outlet requirements for domestic
storage cisterns

Outlets from a cistern include indirect cold water distribution pipes and cold
feed pipes to hot water storage systems.
Figure 5.47 shows the positioning of cold water distribution and cold feed pipes.
It is recommended that the cold water distribution pipe be taken from the
bottom of the cistern. This is to prevent the build-up of sediment on the bottom
of the tank; alternatively, the cold water distribution pipe can be located on the
side of the cistern.

The distance between the cold water distribution outlet and the cold feed to the
hot water system should be not less than 25 mm.

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