Page 430 - 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

Expansion vessel
Mains cold water supply Expansion relief valve
Temperature relief valve
Isolation valve
In-line strainer

Pressure reducing valve
Balanced cold
connection
Single check valve
Tundish

Discharge pipework

p Figure 6.58 Installation of shower mixing valves from an unvented hot water storage cylinder

Installations that use supplies where there is an
imbalance in supply pressures (instantaneous hot
water heaters/combi boilers)
Showers installed on instantaneous water heaters and combination boilers
require a shower valve that is pressure compensating. This is because as the cold
water passes through the hot water heater/combi boiler, it loses pressure and
flow rate, and so an imbalance of pressure/flow rate between the mains cold
water and the hot water from the heater occurs. The pressure-compensating
shower mixer valve adjusts both pressure and flow rate within the shower valve
body to give a reasonably powerful shower.

Water heater

Pressure-compensating
shower valve

Isolation valves

Mains cold water inlet

p Figure 6.59 Installation of a pressure-compensating shower mixing valve

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