Page 299 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 5 Cold water systems

should be fitted onto the same cistern as the float-operated valve. Both cisterns
must be of the same size and capacity. INDUSTRY TIP

When connecting two or more cisterns, care should be taken to ensure that the A free copy of the Water
water movement is regular and even across all cisterns. In this situation, it is a Supply (Water Fittings)
good idea to install float-operated valves on all cisterns with appropriate service Regulations 1999 can
valves, as detailed in the Defra guidance to the Water Supply (Water Fittings) be downloaded from the
Regulations 1999: relevant government pages
Service valves should be fitted as close as is reasonably practical to at: www.legislation.gov.uk/
float-operated valves. uksi/1999/1148/contents/
made
Wherever a float-operated valve is fitted, then an overflow/warning pipe must
accompany it. These should terminate in a conspicuous, visible position outside
the building. On no account should they be coupled together.
There should be service/gate valves positioned to allow for isolation and
maintenance of the cisterns without interrupting the supply. In Figure 5.53, you
will see that any two of the four cisterns can be decommissioned, leaving two in
operation. This ensures continuation of supply.

Every cylinder has a float-operated valve to allow movement of water in every cylinder
Each FOV is fitted with a service valve as detailed in the Water Supply (Water Fittings) Regulations

All FOV's to shut
off at the same
water level

Gate valves to be positioned so that any Every cylinder to have its own
two cisterns can be de-commissioned for independent overflow/warning pipe.
cleaning and maintenance, leaving These should evacuate the building
two in commission for supply separately and NOT be joined together

p Figure 5.53 Installing three or more cisterns

Break cisterns

Break cisterns (often called break tanks) are used in large cold water
installations in order to supply the system with water via a set of boosting
pumps when the mains supply is insufficient. They provide a ‘break’ in the
supply between the mains supply and the installation. This has several
advantages over pumping direct from the mains supply:
● Using break cisterns ensures that there is no surge on the mains supply when
the boosting pumps either start or stop.
● Break cisterns ensure that contamination of the mains cold water supply
from multi-storey installations does not occur.
● Break cisterns ensure that there is sufficient supply for the installation
requirements at peak demand.
● Break cisterns safeguard the water supply to other users by not drawing large
amounts of water from the mains supply through the boosting pumps.

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