header/expansion tank keeps filling

[optimist]

We moved house a couple of months ago and in the last few days have noticed that the inlet on my header/expansion tank runs continuously. It doesn't overflow but just seem to keep trickling into the central heating system (in fact the water level never gets anywhere near the overflow). As soon as i raise the ball cock it stops so i don't think it's the washer. Does that mean that there is a leak because all that water must be going somewhere?

 

[chrishutt]

Does that mean that there is a leak because all that water must be going somewhere?

Congrats. You have reached NVQ level 2. Do you have any pipework under a ground floor or anywhere else where a leak might not be noticed?

 

[optimist]

Thanks for replying. Ground floor is a mixture of floorboarding and concrete scree due to property being extended. I presume from your reply that I am on the right track so tomorrow will start with the wooden flooring and then the concrete! Problem can't be ignored as the expansion tank level drops a few mm in a few minutes if I hold up the ball cock. I don't suppose there is something along the lines of rad-weld that might seal the elusive leak? Are their devices to listen for leaks that a plumber may be able to come and use before I start to randomly use the sledge hammer?

 

[scatmanjohn]

Check under the floor boards first. There is such a thing as leak sealers but i doubt that it will stop your leak. It might be worth a try if you can not find it though

 

[JohnD]

Before you climb under the flooboards, open up a little gap and have a sniff in a few corners. You can often smell damp concrete, especially if it's got builders' rubbish under there.

 

[ChrisR]

open up a little gap

and look for steam!!

 

[chrishutt]

and look for steam!!

He really means water droplets suspended in the air, like you get above the spout of a kettle or over a hot bath. Steam is invisible.

 

[optimist]

Thanks for all the advice. I'll let you know if and how I locate it.

 

[Soggy_weetabix]

Fernox internal stuff (in my experience) will do a small leak, but I have 'triple dosed' a system with 7 rads on a sealed system and sealed a 1 bar drop over a few days.

I considered that quite a considerable leak, but it was easiest option on all copper screeded system.

David

 

[optimist]

Found the leak, under floorboards. Pipe was in contact with concrete and had corroded through. I drained system and repaired. Refilled and bled radiators but now the boiler keeps over heating and cutting out. It's a Potterton Suprima 70L. Is it likely that there is air stuck somewhere? If so where do I bleed it?