Expansion Discharge - GAH Electrastream User And Installation Instructions Manual

4-5

Expansion Discharge

AIR BREAK
DISCHARGE PIPE
Fig. 4-5a Tundish
Note
The TPRV and PRVs must not be used for
any other purpose.
WARNING
Scalding water and steam can be
blown out of the discharge pipe.
Position the discharge so that it is
not a hazard to property or people
(especially children).
4-5.1 Tundish
The Tundish must be vertical and fitted within 500mm of the temperature and pressure
relief valve and must be located with the cylinder. The tundish must also be in a position
visible to the occupants, and positioned away from any electrical devices. 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, and to be of metal.
4-5.2 Expansion Discharge - Self Sealing Valve
A Hepvo Self Sealing Valve is available as an option, this enables alternative discharge
arrangements to be used, however its use and installation must be approved by the local
building control.
4-5.3 Expansion Discharge Pipe - To Gully
See Fig.4-5b
Discharge pipes from the TPRV and PRV may be joined together.
The pipe diameter must be at least one pipe size larger than the nominal outlet size of the
safety device, this is adequate when the hydraulic resistance does not exceed that of a
straight pipe 9m long.
Bends must be taken into account in calculating the flow resistance.
Minimum pipe sizes are given in Table 1, overleaf.
The discharge pipe must have a vertical section of pipe at least 300mm in length, below
the tundish before any elbows or bends in the pipework.
The discharge pipe must be installed with a continuous fall.
The discharge must be visible at both the tundish and the final point of discharge, but
where this is not possible or practically difficult; there should be clear visibility at one or
other of these locations. Examples of acceptance are:-
1. Ideally below a fixed grating and above the water seal in a trapped gully.
2. Downward discharges at a low level; i.e. up to 100mm above external surfaces
such as car parks, hard standings, grassed areas etc. These are acceptable
providing that where children may play or otherwise come into contact with
discharges, a wire cage or similar guard is positioned to prevent contact, whilst
maintaining visibility.
3. Discharges at high level; i.e. into a metal hopper and metal downpipe 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 3m from any plastic
guttering systems that would collect such a discharge (tundish visible).
4. 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. Note: The
discharge will consist of scalding water and steam. Asphalt, roofing felt and non-
metallic rainwater goods may be damaged by such discharges.
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