central heating leak...IS IT THE BOILER?

[mark al]

HI, ive recently had a worcester bosch combi boiler fitter(24i junior) by a corgi fitter who seemed very good if very expensive. the problem is the pressure is dropping from week to week and requires topping up. we have tried to locate the leak in pipework up to the rads but to no avail. i have checked the pipes entering the boiler at the bottom but these appear fine. the wall immediately below the boiler is slightly damp and it would seem logical to assume some connection between this and the pressure drop but as i have said i can seen no sign of leakage from the boiler . am i missing something ? are there any pipes further up in the boiler that could be causing this? any help or advice would be really welcome.

[Andrew Gabriel]

Are there any isolation valves in the circuit, for example, on the pipes going in to the boiler? You could close them all (with the boiler completely powered off of course, not even frost protection) and try and work out which section is losing pressure. If there are isolation valves on entry to the boiler and the pressure guage is in the boiler so it will be measuring the pressure in that isolated section, and the pressure still drops, there you have it. (If the system's pressure vessel isn't in the boiler, the drop in this situation will be very quick, although you would have to measure this when the boiler had completely cooled down, as any further cooling would give a misleading exaggerated pressure drop too.)

[Ed Sirett]

Could be the pressure releif valve in the boiler - see FAQ below.