Page 304 - 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

Stop Industrial process
valve with a fliud
category 4 risk
Gate
valve

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

Stop valve
Water undertaker's cold
water mains supply
p Figure 5.57a Zoned protection

Stop
valve

RPZ valve protection
on each floor (zone)
Stop
valve

RPZ valve protection
on each floor (zone)
Stop
valve

RPZ valve protection Cold water supplies to
on each floor (zone) individual apartments
from a common
supply pipe
Stop
valve
RPZ valve protection
on each floor (zone)
Stop valve

Water undertaker's cold water supply
p Figure 5.58 Zoned protection for domestic premises

Point-of-use protection

This is the simplest form of backflow protection. Point-of-use backflow
protection devices are used to protect an individual fitting or outlet against
backflow and are usually located close to the fitting they protect, such as
a single check valve on a mixer tap to protect against fluid category 2, or a
double check valve on a domestic hose union bib tap as protection against fluid
category 3.

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