the overflow pipe is leaking, how do i fix this?

Hello Sue, I have exactly the same problem. I've had three plumbers look at it, and none have got back to me with a solution, so..
Starting at the beginning, can you find where the leak is coming from? If it is an old central heating system, you will have two tanks in your loft, one sits above your hot water cylinder (cold feed) and the other is a smaller tank next to the cold feed tank, which caters for feeding/expansion of the heating loop from the boiler. (It is this f/e tank that is overflowing in my case). Once you have found which tank is overflowing, check the ballcock which provides water to that tank, it is common for these to degradate over time and start to leak. If so, change the ballcock, problem solved!
If only it was always that easy! . Now the rest of the info I can give you works on the fact that it is your f/e tank that is overflowing, (my problem). The next thing to check is that the hotwater cylinder thermostat and the boiler thermostat are working okay. Turn the setting down to see if the leak stops. Another thing to check is that all your radiators are getting hot, if not, you have a blockage and this could be causing the system to backfill. (I found this to be the case with mine last night, so I will take that radiator off today to see if it fixes the problem). If not i'm back to the yellow pages!

Ian
March 2008