Page 432 - 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

When both hot and cold supplies are fed from a cistern, no backflow protection is required.
However, when both are fed from mains-fed supplies, then single check valves are required with a
Shower valves hose retaining ring to prevent the hose entering the water. If no retaining ring is fitted, then both hot
Fluid cat. 2 and 3 risk and cold supplies should have a double check valve installed.
Electric shower units A double check valve is required where a hose retaining ring is not fitted.
Fluid cat. 2 and 3 risk

The installation of other common

components (taps, valves, pumps,
cisterns and appliances)

Many of the components and appliances installed on hot water systems are
generic and share common installation techniques with cold water systems.
These were dealt with in Chapter 5, Cold water systems.

Testing and commissioning of hot water systems
Testing and commissioning of hot water systems is probably the most
important part of any installation, as it is here that the system design is finally
put into operation. For an installation to be successful, it has to comply with
both the manufacturer’s installation instructions and the regulations in force. It
also has to satisfy the design criteria and flow rates that have been calculated
and the customer’s specific requirements.
Testing and commissioning performs a vital role and its importance cannot be
overstated. Correct commissioning procedures and system set-up often make
the difference between a system working to the specification and failing to
meet the required demands.

In this part of the chapter, we will look at the correct methods of testing and
system commissioning.

Information sources required to complete commissioning work
on hot water systems
Inadequate commissioning, system set-up, system flushing and maintenance
operations can affect the performance of any hot water system, irrespective
of the materials that have been used in the system installation. Building debris
and swarf (pipe filings) can easily block pipes, and these can also promote
bacteriological growth. In addition, excess flux used during installation can
cause corrosion and may lead to the amount of copper that the water contains
exceeding the permitted amount for drinking water. This could have serious
health implications and, in severe cases, may cause corrosion of the pipework,
fittings and any storage vessel installed.

It is obvious, then, that correct commissioning procedures must be adopted if
the problems stated are to be avoided. There are four documents that must be
consulted:

1 the Water Supply (Water Fittings) Regulations 1999
2 British Standard BS 6700 and BS EN 806 (in conjunction with BS 8558)

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