Page 434 - 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

and the pipes are running at full bore. Trickle filling can encourage air locks
to form, causing problems later during the fill stage.
l Unvented systems: before an unvented hot water storage system is filled, the
pressure at the expansion vessel (if fitted) should be checked with a Bourdon
pressure gauge to check the pre-charge pressure. Unvented hot water storage
systems should be filled with all hot taps open. This is to ensure that pockets of
air at high pressure are not trapped within the storage vessel as this can cause
the system to splutter water, even after the system has filled. Water should
be drawn from every hot water outlet to evacuate any air pockets from the
system. The taps can be closed when the water runs freely without spluttering.
The temperature and pressure relief valves should be opened briefly to ensure
their correct operation and to test the discharge pipework arrangement.
● When the system has been filled with water it should be allowed to stabilise
to full operating pressure. Any float-operated valves should be allowed to
shut off. The system will then be deemed to be at normal operating pressure.

Once the filling process is complete, another thorough visual inspection should
take place to check for any possible leakage. The system is then ready for
pressure testing.

Soundness testing hot water systems
The procedure for soundness testing hot water systems is described in
BS EN 806 and the Water Supply (Water Fittings) Regulations. There are two
types of test:

1 testing metallic pipework installations
2 testing plastic pipework systems.
Both of these test procedures are covered in detail in Chapter 5, Cold water
systems.

Flushing procedures for hot water systems and components
Again, this subject was covered in detail in Chapter 5, Cold water systems,
but differs slightly in this case because of the appliances and equipment
installed on hot water systems.

Like cold water installations, the flushing of hot water systems is a requirement
of the British Standards. All systems, irrespective of their size, must be thoroughly
flushed with clean water direct from the water undertaker’s main supply before
being taken into service. This should be completed as soon as possible after the
installation has been completed to remove potential contaminates, such as flux
residues, PTFE, excess jointing compounds and swarf. Simply filling a system and
draining down again does not constitute a thorough flushing. In most cases, this
will only move any debris from one point in the system to another. In practice,
the system should be filled and the water run at every outlet until the water runs
completely clear and free of any discolouration. It is extremely important that
any hot water storage vessels and cold water storage cisterns should be drained
down completely.
It is generally accepted that systems should not be left charged with water once
the flushing process has been completed, especially if the system is not going to

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