Page 290 - 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

Cisterns must be installed to these requirements if the problems of
contamination are to be avoided. In the past, when cisterns were fitted with
unscreened overflows and poorly fitting lids, insects and small mammals could
easily gain access to the water the cisterns contained. Some insects, like mosquito
larvae, need water to complete their life cycle and these must be avoided.
Schedule 2, Paragraph 16, therefore sets out to prevent this, both in the
manufacture and the installation of the cistern.
Correct installation will, in most cases, eliminate the problems mentioned,
especially when avoiding the problem of stagnation of water.

Insulation against BS 1212 part 2 Neoprene rubber sealing
heat and cold float-operated valve grommet around vent pipe
Closely fitting lid
Screened vent
50 mm float valve
connection
25 mm distance between
Service Water level FOV and overflow
valve 25 mm distance between
overflow and water level
Screened overflow/warning
Full-way pipe clip below the water level
gate valve Cold feed to hot water storage cylinder
Cold distribution pipe 25 mm Full-way
25 mm gate valve

p Figure 5.43 Cistern complying with Schedule 2, Paragraph 16, of the Water Regulations

Types of domestic cistern, up to 1000 litres

● Storage cistern: this is designed to hold a supply of cold water to feed
appliances fitted to the system. On indirect cold water systems, storage
cisterns are used. It supplies cold water only.
● Feed cistern: this can be identical to the storage cistern. However, it holds
only the water required to supply the hot water storage vessel. In other
words, it supplies cold water to a hot water storage system.
● Combined storage and feed cistern: this is a combination of the previous
two examples. It is used on an indirect system of cold water where only the
drinking supply is taken direct from the main and the rest of the water is
supplied from a cistern. It stores water for the domestic hot water system
and the indirect system of cold water to the appliances, wash hand basin,
bath, WC, washing machine, etc.
● Feed and expansion cistern: used to feed a vented central heating system;
also allows expansion of water into the cistern when the system is hot.
● WC and automatic urinal flushing cisterns: used to clear the contents of a
WC or urinal. The water they contain is not considered wholesome. They will
be covered in more detail in Chapter 9, Sanitation systems.

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