how to fix domestic hot water?

Check the small feed tank in the loft,or at the highest point,it may have run dry.Check the ballcock has not stuck in the up position,if it has give it a gentle shake it should drop and water should start running into the tank.
Also check the flow and return to the hot water cylinder,there may be some kind of air release valve valve on the fllow for airlocks.
If neither of these are the fault it`ll be the zone valve.

Gasman
September 2008

we need more info than that.
is it a fully pumped system ?
how many motorised valves have you ?
is the tank stat calling for heat ?
etc

hi-spec plumbing & heating (essex)
September 2008