Page 420 - 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

l Washbasins: careful consideration must be applied to washbasin
installations because this is probably the only appliance used in domestic
dwellings where the user puts their hands directly in the running water
without waiting for the water to get hot. When the water reaches
maximum temperature, scalding can occur. Therefore, typical temperatures
between 38°C and 41°C can be used, depending upon the application.
Again, NHS guidelines recommend a temperature of no more than 41°C.
l Bidets: a maximum of 38°C should be used with bidet installations.
● Kitchen sinks: this is probably the area where the user is most at risk.
The need to ensure that bacteria and germs are killed, and that grease is
thoroughly removed, dictates that a water temperature of between 46°C
and 48°C is used. However, as the kitchen is an area with no published
recommendations on hot water temperature, a safe temperature similar
to that of washbasins should be considered, to lessen the risk of scalding
unless notices warning of very hot water are used.

Thermostatic mixing valve Bath

Isolation valve

Isolation valve

p Figure 6.52 A single thermostatic mixing valve installation

Group mixing

Installations where a number of appliances of a similar type are fed from a
single TMV are allowed in certain installations. However, installations of this
type are not recommended where the occupants are deemed to be at high risk,
such as in nursing homes. If a group installation is to be considered, then the
points listed below should be followed.
● The operation of any one appliance should not affect others on the run.
● When one TMV is used with a number of similar outlets, the length of the
pipework from the valve to the outlets should be kept as short as possible
so that the mixed water reaches the furthest tap within 30 seconds.

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