Page 323 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 5 Cold water systems

Pipeline colour codes to BS 1710

Wholesome
drinking water Green - Blue - Green

Hot water
supply Green - White - Crimson - White - Green
KEY POINT

Reclaimed water Green - Black - Green Blue medium-density
polyethylene (MDPE)
water supply pipe must
Effluent Black not be used under any
circumstances to convey
anything other than
Chemical dosing Violet
wholesome drinking
water, nor must it be
Fire fighting Green - Red - Green used to form ducts for
conveying pipes with any
other fluids or cables.
p Figure 5.86 Pipeline colour codes to BS 1710

10 INSTALLING COLD WATER

SYSTEMS AND COMPONENTS

The working principles of taps, valves
and other terminal fittings

Taps and valves can be divided into five separate categories:

1 isolation valves
2 float-operated valves
3 terminal fittings
4 drain-off valves
5 shower mixer valves.
In this part of the chapter, we will look at each one in turn, including the types
available, their uses and the working principles.

Isolation valves and drain valves
As already stated, the main use of an isolation valve is to turn off (isolate)
either complete systems, or parts of a system or appliances. They can be
divided into four distinct types:
1 those that isolate high-pressure systems, such as stop taps
2 those that isolate low-pressure systems, such as full-way gate valves
3 those that isolate appliances and terminal fittings on either high- or
low-pressure systems
4 those that are used for draining down systems.

Stop taps/valves (high-pressure isolation) to BS 5433 or BS 1010
Stop taps are designed for isolation of high-pressure cold water systems
and, because of their restrictive internal design, should not be used on
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