Page 566 - 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

● Where a branch connection into a stack is between 82 mm and 160 mm in
diameter (e.g. a WC branch), no other connection is allowed to be installed
opposite for a distance of 200 mm vertically downwards. The left-hand
drawing in Figure 9.6 shows the restricted area shaded.
● The middle drawing shows that side connections at 90° to the branch are allowed.
● Where the branches are of similar size – say, two 40 mm connections – then
the restricted distance will depend upon the size of the main stack:
● on a stack up to 82 mm in diameter, no connection is allowed for a
distance of 90 mm
● on a stack up to 110 mm in diameter, no connection is allowed for a
distance of 110 mm
● on a stack up to 160 mm in diameter, no connection is allowed for a
distance of 250 mm.

Where it is not possible to meet the requirements of the primary ventilated
stack (e.g. excessive waste pipe lengths), then extra ventilation to the system
will need to be added to safeguard the trap seal. This can be done by installing
either of the following:

● a ventilated branch discharge system, where each waste pipe branch is
separately ventilated
● a secondary ventilated stack system, where the waste stack is directly
ventilated.
These are described below.

The ventilated branch discharge system

Main ventilating stack

Branch ventilating pipe
Rodding eye

Branch discharge pipe
Branch ventilating pipe

Main discharge stack

To sewer
p Figure 9.7 Ventilated branch discharge system
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