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EN
TECHNICAL CHARACTERISTICS
G3 REQUIREMENTS AND GUIDANCE - UK ONLY
Discharge pipe from safety valves
FR
The Building Regulation G3 requires that any discharge from an unvented system is conveyed to
where it is visible, but will not cause danger to persons in or about the building.
The tundish and discharge pipes should be fitted in accordance with the requirements and guid-
ance notes of Building Regulation G3. The G3 Requirements and Guidance sections 3.50 - 3.63 are
detailed below.
For discharge pipe arrangements not covered by G3 Guidance advice should be sought from your
NL
local Building Control Officer.
Main characteristics :
•
Any discharge pipe connected to the pressure relief devices (Expansion Valve and Tempera-
ture/Pressure Relief Valve) must be installed in a continuously downward direction and in a
frost free environment.
ES
•
Water may drip from the discharge pipe of the pressure relief device.
•
This pipe must be left open to the atmosphere.
•
The pressure relief device is to be operated regularly to remove lime deposits and to verify that
it is not blocked.
A typical discharge pipe arrangement is shown further on.
IT
General remarks
•
Discharge pipe-work D2 can now be a plastic pipe but only pipes that have been
tested to a minimum 110°C must be used.
•
Discharge pipe D2 can now be plumbed into the soil stack but only soil stacks that
DE
can handle temperatures of 99°C or greater should be used.
Extract from "The Building Regulation G3" :
Discharge pipe D1
3.50
Safety devices such as temperature relief valves or combined temperature and pressure and
pressure relief valves (see paragraphs 3.13 or 3.18) should discharge either directly or by way of a
PL
manifold via a short length of metal pipe (D1) to a tundish.
3.51
The diameter of discharge pipe (D1) should be not less than the nominal outlet size of the tem-
perature relief valve.
3.52
Where a manifold is used it should be sized to accept and discharge the total discharge from the
discharge pipes connected to it.
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3.53
Where valves other than the temperature and pressure relief valve from a single unvented hot
water system discharge by way of the same manifold that is used by the safety devices, the ma-
nifold should be factory fitted as part of the hot water storage system unit or package.
Tundish
3.54
The tundish should be vertical, located in the same space as the unvented hot water storage sys-
tem and be fitted as close as possible to, and lower than, the valve, with no more than 600mm of
pipe between the valve outlet and the tundish.
Note: To comply with the Water Supply (Water Fittings) Regulations, the tundish should incorporate a
suitable air gap.
3.55
Any discharge should be visible at the tundish. In addition, where discharges from safety de-
vices may not be apparent, e.g. in dwellings occupied by people with impaired vision or mobi-
lity, consideration should be given to the installation of a suitable safety device to warn when
discharge takes place, e.g. electronically operated.
en
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Smart ME : A1003499 - 661Y2000 • C
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