Worked Example Of Discharge Pipe Sizing - andrews STOR-SS300-8-S Installation And Service Manual

6 Installation
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(b) be a separate branch pipe with no sanitary
appliances connected to it;
(c) if plastic pipes are used as branch pipes carrying discharge
from a safety device they should be either polybutylene (PB) to
Class S of BS 7291-2:2006 or cross linked polyethylene (PE-X)
to Class S of BS 7291-3:2006; and
(d) be continuously marked with a warning that no sanitary
appliances should be connected to the pipe.
Note
1. Plastic pipes should be joined and assembled with
fittings appropriate to the circumstances in which they are
used as set out in BS EN ISO 1043-1.
2. Where pipes cannot be connected to the stack it may
be possible to route a dedicated pipe alongside or in
close proximity to the discharge stack.
Termination of discharge pipe
3.61 The discharge pipe (D2) from the tundish should terminate
in a safe place where there is no risk to persons in the vicinity of
the discharge.
3.62 Examples of acceptable discharge arrangements are:
(a) to a trapped gully with the end of the pipe below a
fixed grating and above the water seal;
(b) downward discharges at low level; i.e. up to 100mm above
external surfaces such as car parks, hard standings, grassed
areas etc. are acceptable providing that a wire cage or similar
guard is positioned to prevent contact, whilst maintaining
visibility; and
(c) discharges at high level: e.g. into a metal hopper and metal
downpipe with the end of the discharge pipe clearly visible or
onto a roof capable of withstanding high temperature discharges
of water and 3m from any plastic guttering system that would
collect such discharges.
3.63 The discharge would consist of high temperature water and
steam. Asphalt, roofing felt and non- metallic rainwater goods
may be damaged by such discharges.

6.2.5 Worked example of discharge pipe sizing

Fig. 12: shows a G1/2 temperature relief valve with a discharge
pipe (D2) having 4 No. elbows and length of 7m from the tundish
to the point of discharge.
From Table 6:
Maximum resistance allowed for a straight length of 22mm
copper discharge pipe (D2) from a G1/2 temperature relief valve
is 9.0m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m each =
3.2m.
Issue 1 06/02/20