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7. Discharge arrangement.
Tundishes must be installed in a position so that they are clearly visible by the user. In addition,
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 normal outlet size of the safety device unless its total
equipment hydraulic resistance exceeds that of a straight pipe 9 m long, i.e. discharge pipes
between 9 m and 18 m equivalent resistance length should be at least two sizes larger then the
normal outlet size of the safety device, between 18 m and 27 m at least three sizes larger and so
on. Bends must be taken into account in calculating the flow resistance. Refer to the diagram,
tables and worked example detailed in Fig 6.
(b) Have a vertical section of pipe at least 300 mm 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 Tundish and the final point of discharge, but where this is not
possible or practically difficult, examples of acceptable discharge arrangements are:
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Ideally below a fixed grating and above the water seal in a trapped gully
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Downward discharge at low level, i.e. up to 100 mm 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.
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Discharge at 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 3 m from any plastic guttering
system that would collect such discharges (Tundish visible).
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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 six systems so that any installation
discharging 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 stored systems are installed where discharges from
safety devices may not be apparent i.e. in dwellings occupied by blind, or disabled
people, consideration should be given to the installation of an electrically operated
device to warn when discharge takes place.
Warning Notice –
The discharge will consist of scalding water and steam. Asphalt, roofing felt
and non-metallic rainwater goods may be damaged by such discharges.
