Page 272 - 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

3 As near as possible to the point where the supply enters the building; and,
4 Be so installed that its closure will prevent the supply of water to any
point in the premises.
Source: Section 4, G10.5

The diagram in Figure 5.22 illustrates the point.

150mm

75mm service duct sealed at both ends
No other service or cable in duct

p Figure 5.22 The entry of the water supply to a property

The water authorities recommend that no more than 150 mm of blue MDPE
pipe be exposed above the floor level of the building. This is to minimise the
amount of MDPE pipework visible because MDPE decomposes under persistent
exposure to the ultraviolet (UV) light present in daylight.

There are many different stop valve/tap styles available that are manufactured
to BS 1010-2. This, however, would not be acceptable when used as the lower
stop tap on an internal water meter installation as it would be possible to draw
water from the main before the water meter, leading to erroneous metering.

Any stop tap used above or below ground must be made from either gunmetal
or corrosion-resistant brass, to prevent de-zincification of the stop tap. The
Water Regulations state:
Every water fitting shall be immune to or protected from corrosion
by galvanic action or by any other process which is likely to result in
contamination or waste of water.

Source: Schedule 2, Reg. 3
All fittings that are made of a copper alloy, such as brass or gunmetal, should
carry either ‘CR’ or ‘GM’ markings on the fitting body to show that they are
corrosion resistant.
A drain-off valve conforming to BS EN 1254 should be installed immediately
above any stop tap/valve to allow draining of the system.
260

9781510416482.indb 260 29/03/19 8:57 PM