GUIDANCE NOTES
TUNDISH DISCHARGE
The unit is supplied with two mechanical safety devices. An expansion relief valve, supplied loose, and a temperature/pressure relief valve fitted to the unit, both discharging into a tundish (supplied loose).
Discharge pipes must be left open to atmosphere, not blocking the tundish.
The responsibility for supplying and fitting the discharge pipe from the tundish is that of the certified installer. In general, installation practice should be in accordance with the approved document G3 of schedule 1 of the building regulations 1991, VIZ:
3.9The 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:
aBe 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 larger than the nominal outlet size of the safety device, between 18m and 27m at least 3 sizes larger, and so on. Bends must taken into account in calculating the flow resistance. See Diagram and table on page 6.
bHave a vertical section of pipe at least 300mm long, below the tundish before any elbows or bends in the pipework.
cBe installed with a continuous fall.
dHave discharges 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 discharge arrangements are:
d.1 Ideally below a fixed grating and above the water seal in a trapped gully.
d.2 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 may 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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