Page 303 - 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

installation, or even the water undertaker’s mains supply, despite the fact that
the installation is installed to the required standards. In these circumstances,
whole-site or zone protection must be installed on those parts that are deemed
to be high risk.

Whole-site protection
The term ‘whole-site protection’ simply means that the water undertaker’s
main is protected at all times from backflow or back siphonage from any fluid
category that is not fluid category 1 by a suitable backflow device. Protection
should be at the point of entry of the cold water supply.

Industrial process with
a fluid category 4 risk

Reduced pressure zone (RPZ)
valve giving fluid category 4
risk protection to the water
undertaker's main

Stop valve

Water undertaker's cold
water mains supply

p Figure 5.57 Whole-site protection
If whole-site protection is required, it is important that the water undertaker is
informed at the application/notification for water supply stage. They will assess
the application for a water supply and advise on what fluid category of backflow
protection device must be installed to comply with the Water Supply (Water
Fittings) Regulations. The backflow protection device must be installed before
the system is commissioned.

Zoned protection

Zoned backflow protection simply means that, where different fluid categories
exist within the same building, premises or complex, these have their own
backflow protection devices to protect any part of the system that is fluid
category 1. Zoned protection is also required where any water supply pipe is
supplying more than one separately occupied premises.

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