Page 428 - 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

Systems that use a twin impeller pump on the inlet to the mixer valve
The pump increases the pressure of the hot and cold water supplies to the
mixer valve independently. The water is then mixed to the correct temperature
in the valve before flowing to the showerhead.

When water is heated, the air in the
water starts to form around the walls
of the pipe and the cylinder as little
bubbles. By making the connection at

30º−60º the air is allowed to pass
30º−60º through the open vent pipe where it
dissipates over the cistern. If the air
was allowed to get into the shower
pump, it would get trapped around
Connection of cold water
feed to the cylinder is higher the impeller, eventually leading to
than the cold for the shower pump failure
so that the hot water runs Hot connection for
out first the shower taken at

90º to the angled
cylinder connection
An alternative connection
direct to the cylinder
using an Essex flange

22 mm pipe taken as far as possible
before reducing to 15 mm
p Figure 6.56 Pump-assisted shower installation with twin impeller, inlet shower booster pump

Connection of cold water
feed to the cylinder is higher
than the cold for the shower
so that the hot water runs
out first

A connection
direct to the
cylinder using an
Essex flange

p Figure 6.57 Pump-assisted shower installation with single impeller, outlet shower booster pump

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