Combi Boiler Pressure Drop

[johnk]

My combi needs to topped up about every 2 days. This must mean the water is leaking somewhere but there is no sign of a leak on any pipework. Could it be the heating water can somehow leak to the hot water?

[Baldric]

Shouldn't do, heating is a sealed system seperate to HW.

[Mosaic]

Just had a similar problem - something to do with the gasket between two gizmos failing ie the tank that the water passes through and the heating whatist.

[The Builder]

Mine is doing the same, John. I'm currently waiting for them to fit a new pressure relief valve.

Outside, somewhere, you'll see a pipe sticking out of the wall. It's the expansion pipe. Put a milk bottle over the end. I'll bet it fills up the next time the boiler's on.

[The Builder]

Or... The expansion vessel has lost its pressure for some reason. Either way, you do need a boiler man, John.

[johnk]

Thanks everyone, looks like I'll be getting the man in.