Page 620 - 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

KEY POINT Performance testing, step by step
Testing trap seal depth With the soundness test complete and the test equipment removed,

The dipstick is a thin performance testing can begin. This is done to confirm that the system meets
piece of wood painted the recommendations of the British Standards and the Building Regulations.
matt black. It is inserted 1 Fill all of the appliances with water up to their overflow levels and release
down the centre of the water from the appliances simultaneously.
the waste fitting until
it reaches the bottom 2 At the same time, flush the WCs.
of the trap. When it is 3 When all of the appliances have emptied and the WC flushes have finished,
withdrawn, the wetness the traps of all the appliances can be checked for water seal depth. The trap
should be measured and seal depth after all of the appliances have discharged their water must be at
the diameter of the trap least 25 mm. This can be checked with a dipstick.
deducted. What is left is
the depth of trap seal.
Expansion and contraction in sanitary
appliances pipework systems and negative

effects
One of the problems with PVCu soil and waste pipe is the large expansion rate.
This can cause the joints to move as they get warmed by hot water discharging
Depth of
trap seal down them or the Sun and, in extreme cases, can cause joint failure.
Deduct diameter of trap
p Figure 9.108 Testing trap IMPROVE YOUR MATHS
seal depth PVCu has a coefficient of linear expansion of 0.06 mm/m/°C. This means that,
for every metre (1 m) of pipe, PVCu expands by 0.06 mm for every degree rise
in temperature.
For example:
If a 1 m length of pipe is subjected to a rise in temperature of 10°C, it will
expand by the following amount:
1 × 0.06 × 10 = 0.6 mm
This might not seem a lot, but let us look at this in more detail.
Example
A south-facing external soil and vent pipe 10 m high is subjected to a 25°C
temperature rise. What is the expansion of the pipe when the coefficient of
linear expansion of the pipe is 0.06 mm/m/°C?
All the information we need to be able to calculate this is in the question:
Length of pipe = 10 m
Temperature diff. (Δt) = 25°C
Coefficient of linear expansion = 0.06 mm/m/°C
Therefore:

10 × 25 × 0.06 = 15 mm

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