Overflow pipe dripping when heating turned on

[ihavealeak]

Hi, hope someone can help...

I have a small 2bed house, 1980's build. No problems with plumbing since being here.

However, 1 of the overflow pipes has started dripping since I had some work done. In my attic/loft I have 2 tanks, 1 much larger than the other.
The drip is coming from the smaller tank.

It only starts dripping when I put on the central heating or hot water though.

I'm assuming this means that there is nothing wrong with the ball valves inside the tank as it is not filling up to the point of over flowing apart from when I turn on the heating.

If this is correct - then why does it overflow due to hot water/heating? The large cylindrical water tank in the airing cupboard that gets hot must be pushing hot water back up to the loft and into this smaller tank and then out through the overflow pipe? Correct?

Next question is why would it start doing this since I had a plumber come to change the ends on a radiator?!

Any help much appreciated!

Thanks
Nathan

 

[Gary Swart]

The leak is from the T/P valve on the tank. It is opening because the pressure inside the tank increases when the water heats to the danger point. That's what the T/P is supposed to do. This keeps your tank for exploding like a bomb. I assume (dangerous thing to do) that you have a pressure regulator valve on the main water supply line. This blocks the thermal expansion from being absorbed by the city water main. The remedy is to install a thermal expansion tank between the heater and the PRV. As to why it just began to happen, I haven't a clue.