Running water mystery

is it an airlock clearing in a radiator circuit?

"Young man, you have an elemental spirit in your bathroom, and a particularly nasty one" ["From Beyond the Grave"].

Air in the central heating and a sticking ball valve.

When CH is on, air expands forcing water it the expansion tank where it overflows.

At night, CH is off, air cools and contracts. Water is drawn from expansion tank, but due to sticking ball valve, a "sudden" top up of the tank occurs rather than a dribbled one. Try fixing the ball valve up to see if it stops the problem.

Thinking on it, could be a similar mechanism in the hot water system, if there is an air lock. Try fixing both valves on different nights.

Of course, are you sure it is you water you can hear running? If you are in a flat, terraced house or semi it could be a neighbour's!

Brian

Have you got a central heating system which is cycling on and off on a room thermostat? If so, chances are you've got a bit of trapped air in it which moves around every time the pump starts up - causing a bit of gurgling in one of the radiators.

There's no sign of overflow from the ch header, I checked, but I did wonder if the level in the tanker was noticably lower than it was the last time I was in the roof, nearly two years ago so I wasn't sure if I was imagining things. I'd also checked the rads and pump for air with no result.

Must be mine, house is detached. Thanks for all comments. I'll have another look at the header tank and volve.

Peter Johnson explained on 03/02/2006 :

It sounds as if its likely to be a tank which cools down on a night, which causes the water level to contract - which then is topped up by a float valve. Most likely the hot water header tank, as the heating system header tank would (should) not consume any water.

We used to get something similar. Pumping activity in the water main overnight (refilling the reservoir at the top of the hill). Pressure peaks enough to lift ballcock valves for a few seconds. Very high wear-rate on Yorkshire-type washers. Think about changing all ballcocks to Torbeck types.

Torbeck valves are great in bathrooms etc but tend to have a short life in dirty or dusty locations like attics.

I'm not sure what the name of the type of ballcock that I fitted to the c/w storage tank. It is not a tiny little Torbeck, in that it still has a brass arm and large float, but the plastic valve mechanism has a large-diameter diaphram type of washer. Been there for years now, no probs, (touch wood, pdq).

BTW: Yorkshire ballcocks and plastic tanks don't work very well in high pressure areas. The closing force on our tank was limited by bending of the tank walls. Not very much wear on the washer and the float would be fully submerged, but still with a small drip, drip from the valve.

Have you got a toilet that has a button on the top to flush it? We have one of those and ours was exhibiting the same kind of noises. The button was adjusted incorrectly so that it was pushing down slightly on the flush mechanism, which caused it to leak slightly. Hence every now and then it would open the valve to refill the cistern.

Mark.

Now, as it happens ... yes, I have three of them, about two years old. I was suspicious of the one I use most but whilst I couldn't see any sign of leaking/over filling when I took the lid off I didn't get the running water scenario whilst it was off! Thought that was just a coincidence.

Thanks for all the comments on ch header tanks. I have checked mine and the valve seems to be working ok. I have also checked the rads and pump for air and haven't found any. Anything else I should try in case it isn't the wc?

In message , Peter Johnson writes

It's just the hot header tank filling up a bit more because the water pressure has risen because the demand on the mains is minimal. I had a similar problem some years ago, another problem was that if you had a shower after midnight the temperature (flow) control valve in the shower would become unstable and cause water hammer. I even managed to measure it one night at over 6 bar. I fitted a pressure reducing valve at the suggestion of the water-softener suppliers (it was noisy when it regenerated) and the problems went away. I also seem to remember that sometimes you could get a wave moving back and forth in the tank, kept going with little spurts of water from the ball c*ck. I replaced this quaint brass Victorian designed ball valve with a modern American "Fluidmaster" valve (from B&Q).

Yes. That's it. Needs a new sealing washer. Pinned it down when I turned off the service valve and the tank emptied on its own! Thanks for all comments.

How long did it take to empty? That's the trouble with these new devices, they can waste lots and lots of water! Bring back the syphon!

Time to empty varied, sometimes as little as half an hour, sometimes it would take several hours. But over the couple of weeks it took to identify the problem it must have emptied a couple of dozen times, and me on metered water, too! (I rang the people who'd installed this one (nearly two years ago) and their man came round with a new washer/seal for me. I shall get a few in stock now.)

Do you have a primatic hot water cylinder? You will only have the main HW tank in the loft, not the smaller CH top up tank.

These tanks make exactly that noise.