Page 149 - 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 2 Common processes and techniques

From bend 2 to bend 3
The distance here is 350 mm and because there are clips at both bends, the distance between the bends does
not change.
Bend 3 can be marked and bent at the distance of 350 mm.
From bend 3 to bend 4
The distance here is 450 mm and because there are clips at both bends, the distance between the bends does
not change.
Bend 4 can be marked and bent at the distance of 450 mm.

From bend 4 to elbow 2
The distance is 500 mm and because there is an elbow at the end, 12 mm should be deducted for the ‘X’ dimension:

500 − 12 = 488 mm
Therefore, length of pipe:

888 + 890 + 350 + 450 + 488 = 3066 mm or 3.066 m
There are four machine bends on the 15 mm pipe and, as we have seen, these have a pipe gain of 21.5 mm
each. Therefore:

21.5 × 4 = 86 mm. This can be deducted from the total length:
3066 − 86 = actual tube length = 2980 mm or 2.980 m

Many of the appliances we fit arrive on-site prefabricated. Boilers, hot water
storage cylinders and some sanitary ware can be manufactured ‘pre-plumbed’
so that only the final connections have to be made when the unit is put in
position.

Prefabrication techniques can be carried out on most fixed pipework types,
including copper, low carbon steel, and plastic soil and waste pipes. The
techniques will differ depending on the material used.

Sleeving of pipework through walls

Pipes passing through masonry, stone and concrete should be sleeved by a piece
of tube one size larger than the pipe being installed, to allow for expansion and
pipe movement, and to prevent damage to the pipe by building movement. The
sleeve should then be sealed with an approved sealant to prevent the ingress
of rain, insects and vermin. Where gas pipes are sleeved, the sleeve should be
sealed only on the inside of the wall; the outside part of the sleeve should be
sealed only to the building fabric and NOT the pipe. The pipe and sleeve should
be left open.

Working on existing installations: in situ working KEY TERM
Working on existing installations is challenging. There is always a risk of
disturbing joints and causing further problems. Situations often occur where it In situ: in situ, in plumbing
is necessary to cut into existing pipework and it should be treated with care. terms, simply means
pipework or appliances that
Problems can occur when connecting to old imperial-sized pipework when are already in place. They
the pipe sizes differ from new metric fittings and tubes. In situ installation are already ‘in situation’,
operations include: hence the term ‘in situ’.

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