I am having to add water 2 or 3 times a week to our boiler to keep the pressure up.we have had 2 proffesionals look at it in the last 2 years and both say there must be a leak in the system somewhere.I have traced all the pipework twice and the boiler itself,and everything is dry.this is so frustrating as we have put up with it for 3 years now.having spoken to many specialists about it and still drawing a blank I am hoping you can help.

sandie, November 2008

I just wanted to thank Robbo for taking the time to answer my problem.I will follow up your suggestion.
Ta Robbo,

Sandie

sandie, December 2008

This is most likely to be the pressure expansion vessell.
I had the same problem with my boiler.
I would have thought an engineer would have been able to sort this fairly easy though, unless im missing something??
In the excell 80 boiler the expansion vessell is a large round tank at the back of the boiler (usually red)
It is a sealed unit and it has a rubber part in the middle that can crack and perish causing the boiler to over pressure. This then causes the safety valve to lift and release the pressure for safety.
(Check the pipe that runs outside when it loses pressure and see if the wall is damp or wet. This will indicate if the loss of pressure is going through the saftey valve.
Unfortunately because the expansion vessell is a sealed unit it has to be replaced. Not too hard to do if you have a bit of knowledge but the boiler will have to come off the wall as you cant do it in situ on the excell 80.
They are around £60 to £70 to buy from the merchants. They even had mine in stock.

Robbo, December 2008