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10.3.2
RELIEF VALVE DISCHARGE PIPEWORK
It is important that any discharge water does not collect in the discharge pipe-work and can run freely to the
tundish. The Tundish should be mounted in a vertical and visible position located in the same space as the
unvented hot water storage system and be fitted as close as possible and within 500mm of the safety device e.g.
the temperature relief valve.
The discharge pipe from the tundish should terminate in a safe place where there is no risk to persons in the
vicinity of the discharge, be of metal and:
a)
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. discharge pipes between 9m
and 18m 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.
An alternative approach for sizing discharge pipes would be to follow BS6700 Specification for design installation,
testing and maintenance of services supplying water for domestic use within buildings and their curtilages.
b)
Have a vertical section of pipe at least 300mm long, below the tundish before any elbows or bends in the
pipework.
c)
Be installed with a continuous fall.
d)
Have discharges visible at both the tundish and the final point of discharge but where this is not possible
or is practically difficult there should be clear visibility at one or other of these locations.
Examples of acceptable discharge arrangements are:
I.
Ideally below the fixed grating and above the water seal in a trapped gulley.
II.
Downward discharges at a low level; i.e. up to 100mm above external surfaces such as car parks, hard
standings, grassed areas etc. are acceptable providing that where children play or otherwise come into
contact with discharges, a wire cage or similar guard is positioned to prevent contact whilst maintaining
visibility.
III.
Discharges at a high level; e.g. into a metal hopper and metal down pipe with the end of the discharge
pipe clearly visible (tundish visible or not) or onto a roof capable of withstanding high temperature
discharges of water and 3m from any plastic guttering systems that would collect such discharges
(tundish visible).
IV.
Where a single pipe serves a number of discharges, such as in blocks of flats, the number served should
be limited to not more than 6 systems so that any installation can be traced reasonably easily. The single
common discharge pipe should be at least one pipe size larger than the largest individual discharge pipe
to be connected. If unvented hot water storage systems are installed where discharges from safety
devices may not be apparent i.e. in dwellings occupied by blind, infirm or disabled people, consideration
should be given to the installation of an electronically operated device to warn when discharge takes
place.
FIGURE 10.1
RELIEF VALVE DISCHARGE PIPEWORK
500mm MAXIMUM
TUNDISH
METAL DISCHARGE PIPE (D1) FROM
TEMPERATURE RELIEF VALVE
TO TUNDISH
SAFETY DEVICE
(e.g. TEMPERATURE
RELIEF VALVE)
METAL DISCHARGE PIPE (D2) FROM
TUNDISH, WITH CONTINUOUS FALL
FIXED GRATING
TRAPPED GULLY
DISCHARGE IDEALLY BELOW
FIXED GRATING
300mm MINIMUM
Summary of Contents for EcoShield Series
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