just moved into a new house with a heating system thats about 20 years old. all valves perished so in a fit of enthusiasm i drained down the system and took all the radiators off but left the valves.
its a gravity fed system so i tied off the ball valve and the tank is empty. mysteriously, two weeks since initial drain down the system seems to be taking on water - about 5 pints can be drained from the 'flow' valve on a downstairs radiator. (and one upstairs) then the pressure disappears and the water stops. if i leave it for a while the water comes back and i can drain it off again. interestingly this only happens when i open a flow valve, not on the return.
how can water still be getting into the system? could it be a problem with the hot water tank?
Well. I think you're right. The water can only get into the system in two ways. Firstly the header tank. Of course the ball valve may be still dripping, but I assume you have checked that. So that only leaves the cylinder.
Best disconnect the feed pipes and see if water comes out.
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