U
Unregistered
I have a system boiler, when the hot water only is on, the water in the hot return backs up the radiator return loop heating the radiators. the motorised valve on the tank is working fine, the tank thermostat is working, i replaced the heating motorised valve so that is fine. from cold, when the water is turned on, the system return gets hot quickly and immediately backs up the rad return HELP please its driving me spare
