My expansion tank keeps overflowing Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[Mr Mackey]

Hi, before christmas I noticed the garden patio was wet, found it was coming from the overflow pipe just under the guttering and discovered it was linked to the expansion tank. When I first saw it, it seemed the ball valve wasnt shutting off properly so I bought a new one, installed it and thought job done.

It keeps over flowing!!!!! - I have adjusted it the hight of the ball a few times, with the central heating off and with the central heating on at the highest temp but still happening...... Can someone help??

Simon

[plumbbob]

Which tank is over flowing? The big one or the little one?

[kn1ght1]

Sound like your ballcock need replaceing, I had the same trouble with a build up of calcuim inside it so when the should have been off was still passing a dribble of water, adjusted it a few times with no luck.

Quite easy and cheep to replace, just make sure you get the same size (and turn you cold water off at the stop tap), you shouldn't need to drain anything, should cost less than a £5 and take about half a hour to do.

[kn1ght1]

Sorry, meant to say I had to change both ball valves in both my tanks, as they decided to take it in turns to drip, had me scraching my head for ages, dont know if it helps??

[DEEARR2]

Do you have an isolating valve controlling the flow to the expansion tank ballvalve. If so, try filling the f/e tank and then isolate the supply to it. Check if the overflow continues. If it does then it is possible you may have a mix taking place inside the indirect cylinder via the heating coil. This could be the case if the expansion tank is lower than the main staorage tank.

[Mr Mackey]

its the little one, expansion tank for central heating, thanks to knight but my message said i did replace the ball valve...:(

I did another test today, had the heating off for about 3 hours, looked at the tank, drained up to a certain level (just at the max of the ball valve) and then turned on the heating to max. After a few hours I went up to have a look and it had risen by 2 inches. The ball valve is not letting in water.

I know this could mean the hot water has expanded so I will check again after a couple of days but this has been going on since before christmas.

My fear is my hot water is somehow leaking into the central heating (please god no!!!!)

[Steve the gas]

Hi,

Yep, sounds like the coil in the cylinder is perforated = new cylinder, soz

[plumbbob]

Oh dear I think you have a problem with the tank coil.

See this topic

https://www.diydoctor.org.uk/forums/view ... hp?t=15578