Boiler keeps losing pressure, overnight - no leaks on radiators or damp patches anywhere. Have noticed that water is dripping outside - from the pressure relief valve pipe when the heating is running.
What could be the cause of this?

Andy Smith, December 2010

I am having the same problem with my Alpha 28 boiler. I think the problem is a faulty pressure relief vale.

Peeks, February 2011

It's almost certainly a leak from one of the unions of the central heating pipes with the primary heat exchanger. The union is a real weak point, relying on a small o-ring seal and a bendy clip to hold them in place and seal watertight. The o-rings perish over time. They're simple enough to replace.

Olly, February 2011