9
3.3 DISCHARGE
It is a requirement of Building Regulations that any discharge from an unvented
system should be visible and safely conveyed away from the system without
danger to persons in or about the building where it is installed. The discharge
pipe should be fitted in accordance with the requirements and guidance notes
of Building Regulations. Building Regulation G3 Requirements and Guidance
section 3.9 are reproduced in the following sections.
Information Sheet No.33 available from the British Board of Agrement gives
further advice on discharge pipe installation. For discharge pipe arrangements
not covered by G3 Guidance or BBA Info sheet No. 33 advice should be sought
from your local Building Control Officer. The discharge pipework will convey
any discharge from the unvented cylinder Temperature and Pressure Relief
Valve. (A discharge pipe will also be required from the Expansion Valve fitted
to the Cold Water Combination Valve) Where practical this can be feed into the
discharge pipe from the Multipoint SS. It is recommended that an additional
tundish is fitted into this discharge pipe to give an early indication of operation
of the Expansion Valve.
In some instances it may be possible to discharge into an internal waste system
and soil stack. To do this a self sealing waste valve must be fitted into the
discharge pipe after the tundish to prevent foul odours or back-pressurisation
from the waste system entering the building via the tundish. In these systems
it is essential that the tundish is fitted in a visible position as the final point of
discharge will not be visible. Consult the manufacturer’s recommendations
with respect to the correct fitting, orientation and waste and soil stack materials
selection. It will also be necessary to get dispensation from your local Building
Control Officer to discharge in this manner. Discharges from an unvented
system can be up to 95
o
C for several minutes, ensure any waste or soil pipe
connected to the discharge can safely accept these conditions.
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.”
Water may drip from the discharge pipe of the pressure-relief device and that
this pipe must be left open to the atmosphere.