Page 565 - 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 9 Sanitation systems

Branch connections for waste pipes

45°
2.5 diameter

of pipe 87.5° – 67.5°
200 mm
max

50mm radius
Radius not more 200mm
than 25 mm
Permitted
connections
p Figure 9.5 Branch connections

In Figure 9.5, the left drawing shows that junctions, including branch pipe
connections of less than 75 mm, should be made at a 45° angle or with a
25 mm bend radius. The prohibited zone in the right-hand drawing shows
the area (opposite the WC connection) in which a branch pipe may not be
connected to a distance of 200 mm. Branch connection pipes of over 75 mm
diameter must either connect to the stack at a 45° angle or with a minimum
bend radius of 50 mm.

Prevention of cross-flow
A branch pipe should not discharge into a stack in such a way that it could
cause cross-flow into any other branch pipe. This can cause loss of trap seal by
effluent back-flowing up the opposite connection.

Branch diameter Centre line of opposed Small branch
82 mm to 160 mm branch not to be below diameter
this point 82mm max

Unopposed (see
200 mm connection 200mm next
permissible page)
in this area
Section Centre line of opposed Section Section
branch not to be above
this point
Plan Plan

(a) Restricted connection (b) Examples of permitted (c) Opposing waste pipes
area on stack connections
p Figure 9.6 Preventing cross-flow
Figure 9.6 shows the areas of a soil stack where branch connections directly
opposite are restricted. In general, there are several rules, as follows.

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