Issue 1 06/02/20
23
Installation
6
3.55 Any discharge should be visible at the tundish. In addition,
where discharges from safety devices may not be apparent, e.g.
in dwellings occupied by people with impaired vision or mobility,
consideration should be given to the installation of a suitable
safety device to warn when discharge takes place, e.g.
electronically operated.
Discharge pipe D2
3.56 The discharge pipe (D2) from the tundish should:
(a) have a vertical section of pipe at least 300mm long below the
tundish before any elbows or bends in the pipework and
(b) be installed with a continuous fall thereafter of at least 1 in
200.
3.57 The discharge pipe (D2) should be made of:
(a) metal; or
(b) other material that has been demonstrated to be capable of
safely withstanding temperatures of the water discharged and is
clearly and permanently marked to identify the product and
performance standard (e.g. as specified in the relevant part of
BS 7291).
3.58 The discharge pipe (D2) should be at least one pipe size
larger than the nominal outlet size of the safety device unless its
total equivalent hydraulic resistance exceeds that of a straight
pipe 9m long, i.e. for discharge pipes between 9m and 18m the
equivalent resistance length should be at least two sizes larger
than the nominal outlet size of the safety device; between 18
and 27m at least 3 sizes larger, and so on; bends must be taken
into account in calculating the flow resistance.
3.59 Where a single common discharge pipe serves more than
one system, it should be at least one pipe size larger than the
largest individual discharge pipe (D2) to be connected.
3.60 The discharge pipe should not be connected to a soil
discharge stack unless it can be demonstrated that the soil
discharge stack is capable of safely withstanding temperatures
of the water discharged, in which case, it should:
(a) contain a mechanical seal, not incorporating a water trap,
which allows water into the branch pipe without allowing foul air
from the drain to be ventilated through the tundish;
Note
To comply with the Water Supply (Water Fittings)
Regulations, the tundish should incorporate a suitable air
gap.
Note
An alternative approach for sizing discharge pipes
would be to follow Annex D, section D.2 of BS 6700:2006
Specification for design, installation, testing and
maintenance of services supplying water for domestic use
within buildings and their curtilages.
See
See fig. 13
