gledhill BoilerMate A-Class OV SOL Series Design, Installation & Servicing Instructions page 25

INSTALLATION
Note: When fitting the cistern, it must not be more than 6 metres above the base of
the BoilerMate A-Class OV SOL appliance.
The open vent must have a continuous rise from the appliance to its discharge point
above the F&E cistern.
Check and comply with the requirements of the Water Regulations/boiler manufacturer
regarding the arrangement of the open vent.
Obviously, if the feed and expansion cistern is being fitted in the roof space, then
this and the pipework will need to be adequately insulated to protect against frost
damage.
Combined feed and open vent pipe arrangements must not be used.
No valves should be fitted in the safety open vent which must be a minimum of 22mm
copper pipe or equivalent.
The overflow/warning pipe shall have a continuous fall, be fitted to discharge clear
of the building and be sited so that any overflow can be easily observed. It shall also
be installed in a size and material suitable for use with heating feed and expansion
cisterns in accordance with BS 5449 i.e. HT plastic or copper and should not have any
other connections to it.
Page 25