The overflow outside my house is leaking warm water, not sure why as its only just started happening after showing no signs of a problem before. help!!

Steve, Luton, July 2009

Thats no problem Steve - as your boiler heats up the water for domestic use, warm water expands up the pipework and slightly increases the level in the expansion tank, and as it cools down again, the level falls. Thats why the water level in the small tank is usually set to around 6" depth - just enough to cover the expansion and contraction. If for some reason the boiler overheats, then very hot water is shot up the expansion pipe - thats the one that curves over the top of the tank, and splashes into the water already in the tank. In your case, I think that the water level in the tank is simply too high, as its now running out of the overflow pipe, due to the ball valve letting some fresh water to pass. These valves can be rewashered, but I generally fit new ones because they get very little use in normal life.

John, July 2009

Thanks John,

I have just checked the temp of the water (luke warm at best), heating has not been on although i have switched my timer to run ' hot water only' would your answer to my problem still be the same??

Steve, Luton, July 2009

The overflow is leaking from the heating system flow and expansion tank - the smaller one in the loft. You can expect the water to be warm if the heating is on. Check out the ball valve that keeps the tank topped up - chances are the valve is letting a small amount of water through.

John, July 2009