Hi I moved a radiator in my kitchen and when i turned the water supply back on i think the ball valve in the water tank went and i have had a constant flow from the overflow since. Problem is i cant locate the cold water tank. I am a complete noob and its driving me crazy.I live in a new build three storey house with a boiler in the kitchen and a hot water tank in the airing cupboard on the first floor. I thought there would be a cold water tank in the loft but cant locate it. There is a hissing sound of water smilar to a toilet refilling after flushing coming from the airing cupboard which i presume is the sound of the cold water constantly flowing through the pipes. Any help appreciated.
From what you say about he noise in the airing cupboard, the cold water tank could be just above it. In any case, the easiest way to locate it will be to trace the pipe that goes into the bottom of your hot water cylinder and follow it upwards.
You need to locate the central heating header tank, not the hot water header tank, mentioned by the poster above. They are different (unless you live in a very old property with a crude direct system; highly unlikely).
The CH header tank is usually only quite small (holding about 5 gallons/25 litres); the HW header is much larger.. so if you find two header tanks, the smaller one is for the CH.
Have you tried tracing where the overflow pipe goes to? If it comes out of the house wall, or out of the fascia board (just under the guttering), then try to work out where it comes into the house/loft, find it inside and then trace it back. It must end at the tank!
When you do find it, the likelihood is that the ball valve will be stuck full-open. Give it a waggle and it will very likely close and then operate correctly. Because these valves operate so infrequently, when fitted to a CH header, they often get sticky. Other possible causes are: float ball dropped off the end of the arm (it happens!); float ball damaged/puntured (so it no longer floats!); washer/seal at water input damaged; worn valve housing leading to sticking valve spool. If there is doubt, the quickest is usually to buy a complete new float valve assembly and change it. You may need to adjust the water level after fitting the new valve, which is pretty straightforward.
The CH header thank only needs to be about half full.. just so long as the outlet is covered to a depth of a few inches all will be fine.
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