Getting the best from a pressure equalising valve
Reviewed 11 years ago
by David Newton-Dines
These valves work very well WHEN properly used. Do not expect miracles however. It is vital that the pressure ratio does NEVER exceeds 1:20. What this means is that if you have a low pressure hot water system, for example, with say only 2m of head (0.2 bar) then the cold water pressure MUST NOT exceed 4 bar or it will not work.
When you have a low pressure HW system its actually best to fit a PRV (pressure reducing valve) in the cold line and bring it down to something like 2 bar (most are pre set at 3 bar by the way). They perform much better that way.
The last thing to say is that these are designed with a tiny hole in the diaphram so there is some mixing of the hot and cold. So, to comply with Water Regs, they are fitted with non return valves in both lines. DO NOT remove either. To remove the one on the cold risks cross contamination of the cold supply and to remove the one in the hot line means it's possible to back fill the HW cistern and overflow it. YOU HAVE BEEN WARNED.
When you have a low pressure HW system its actually best to fit a PRV (pressure reducing valve) in the cold line and bring it down to something like 2 bar (most are pre set at 3 bar by the way). They perform much better that way.
The last thing to say is that these are designed with a tiny hole in the diaphram so there is some mixing of the hot and cold. So, to comply with Water Regs, they are fitted with non return valves in both lines. DO NOT remove either. To remove the one on the cold risks cross contamination of the cold supply and to remove the one in the hot line means it's possible to back fill the HW cistern and overflow it. YOU HAVE BEEN WARNED.