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?
any suggestions gratefully received!