22
Issue 1 06/02/20
6
Installation
6.2.4 Discharge
It is a requirement of Building Regulation G3 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 guidance notes of Building Regulation G3.
The G3 Requirements and Guidance section 3.50 - 3.63 are
reproduced in the following sections of this manual. For
discharge pipe arrangements not covered by G3 Guidance
advice should be sought from your local Building Control Officer.
Any discharge pipe connected to the pressure relief devices
(expansion valve and temperature/pressure relief valve) must be
installed in a continuously downward direction and in a frost free
environment.
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.
G3 REQUIREMENT
“...there shall be precautions...to ensure that the hot water
discharged from safety devices is safely conveyed to where it is
visible but will not cause danger to persons in or about the
building.”
The following extract is taken from the latest G3 Regulations
Discharge pipes from safety devices
Discharge pipe D1
3.50 Each of the temperature relief valves or combined
temperature and pressure relief valves specified in
3.13 or 3.17 should discharge either directly or by way of a
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 temperature 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.
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 manifold 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 system 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.
See
See fig. 13
