Hi,

A radiator began leaking a few weeks ago so I switched it off and left it because I was going away. When I went away I switched the Central Heating off and now I'm back, it won't work, the central heating I mean. Won't fire up.

To tell the truth last night it did work - but something is amiss and I expect the problem to recur. I bled the radiators; downstairs is OK, but upstairs (where the leaky radiator was) I get a gush of air (in or out?? ) but no water. And the small tank in the loft (rather than the big one I mean) has hardly any water in it.

What could be wrong? I still haven't fitted the new radiator - plan to in a couple of days.

Any ideas?

Best if you call a professional on this one.

I suspect that the small tank in your attic is the expansion tank. Strange, since they're normally near the boiler in a hot-water heating system, but anyway - if it's empty, you don't have to worry about it. Water initially goes into a system cold. When it heats up, it expands, and needs somewhere to go. The water will compress the air in the expansion tank instead of bursting the pipes. If the expansion tank ever gets completely filled with water, you should use the drain valve to let some of the water out (after closing the valve to the rest of the system). New tanks have a rubber diaphragm that prevents that from happening.

As for the heating problem - it sounds like classic airlock. You'd be amazed at how much air can get into pipes if there is a leak. All of that air has to come out before the system will work properly again. Go back to bleeding the upstairs rads, until air stops coming out of them and you get some dribbles of water. Unless there are other leaks in the system that aren't closed off, you're not going to hurt anything.