Page 322 - 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

Methods of preventing cross-connection

in systems that contain non-wholesome
water sources

A cross-connection is a direct, physical connection between wholesome,
potable water and water that is considered non-potable, such as recycled
water or harvested rainwater. In extreme circumstances, this can result
in serious illness and even death. Cross-connections occur during correct
plumbing design and installation, such as the hot and cold connections to a
shower valve or a mixer tap (cross-connection between fluid category 1 and
fluid category 2) and these, for the most part, are protected by the correct use
of mechanical backflow prevention devices. However, some modern plumbing
systems require much more thought and planning, rather than simply the
installation of a check valve. The Water Supply (Water Fittings) Regulations
1999 demand that cross-connections from a water undertaker’s mains to
recycled and rainwater harvesting systems and even connections to private
water supplies are eliminated completely in order to safeguard the wholesome
water supply. There are several ways in which we can do this:
● correct design of systems, taking into account the requirements of the
regulations in place
● careful planning and routing of pipework and fittings
● careful use of mechanical backflow prevention devices and air gaps
● using the correct methods of marking and colour coding pipework and
systems.

Of these, identification of pipework is most important, especially when
additions to the system are required or during routine and emergency
maintenance operations.

Colour coding pipework

All pipes, cisterns and control valves that are used for conveying water that
is not considered to be wholesome must be readily identifiable from pipes or
fittings used with a potable water supply. There are two ways in which this
can be achieved:
1 by the use of labels or colour banding pipes in accordance with BS 1710:
Identification of pipelines and services; above-ground pipes and fittings
should be labelled at junctions, and either side of valves, service appliances
and bulkheads
2 by the use of pigmented materials and pipes – British Standards recommend
that a contrasting type or colour of pipework is used to make identification
easier.

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