heating expansion tank overflow (and its not the ballcock) All aspects of plumbing questions and answers, help, tips and information

[brightspark]

Hi Everyone,

Newby here and I'm in trouble. Just lost my job - house up for sale and my overflow pipe is rapidly turning into a torrent!
I have a gravity fed open air system with two tanks in the attic. The smaller tank feeding the oil fired heating system is overflowing. I replaced the ballcock valve but the extra water is coming from the expansion overflow circulating back into the top of the tank. Sometimes the whole tank is full of hot water. The heating system is switched off for the summer so i presumed it was the hot water system not turning itself off. I repaced the thermostat on the hot water cylinder - no change. The overflow now happens even when the hot water timer is turned off. I dont understand what could be pressurising the system to push water up into the attic?

Can anyone help?

Brightspark

[tomzarblue]

hi
I have come across this problem before, and it occurs when the heating coil in the hot water cylinder gets a hole in it, which allows cold water from your other loft tank to enter. The two tanks are now connected and their contents try to level off to the highest tanks level ie the cold water storage tank, which is above the overflow level in the feed and expansion tank.

In my opinion, a new HW cylinder is the remedy.

Regards Tomzarblue

[brightspark]

Thanks for the advice Tomzarblue.... my brother-in-law said the same thing. Will let you know outcome after I have spent a load of money!

Brightspark

[billobach181]

I had this problem with a friend's water system when the hot water cylinder vented hot water into the cold water supply tank in the attic.
The cause of his problem was that the Thermostatic Shower Valve was not a tight shut off and hot water leaked accross the seats and back filled the cold water storage tank. We changed the shower valve and problem was solved.
So if you have a thermostatic Valve check its operation.
Bill