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Combi Boiler Losing Pressure

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Sue_Balou | 17:33 Tue 05th Jan 2016 | How it Works
3 Answers
We have a 10 year old Worcester 28 CDi combi boiler that has started to lose pressure. It lasts 10-14 days before it needs repressurising.

It started 4 weeks ago when we had no heating/hot water. Called a local Gas Safe chap who said we needed a new expansion vessel. This has been fitted externally but since then we've had the gradual loss of pressure problem. It also takes much longer to repressurise the boiler than it used to, not sure if this is relevant or not. Also, the boiler is located in the attic so it's not easy to check/repressurise.

Before this we would have to repressurise the boiler about 2-3 times a year.

I have called the Gas Safe man and he said he would call on Thursday to "check to work he did" and he thought we had a leak.

So, how likely is it that a new leak would develop at the same time as the external expansion vessel was fitted? Is there anything else that could cause this problem? We haven't bled the radiators recently.

We have 6 radiators all with TRVs and one bathroom.

Just want to be prepared and try to understand what's going on.
Any guidance would be appreciated.


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hi sue i have the same problem as you but i have found the leak it is being fixed seems losing pressure a leak is the 1st thing to look at...good luck
I've just had mine repaired this morning, Sue. Same problem.

Pressure relief valve. Most common cause. A faulty valve will open up at too low a pressure ... shooting the water out of the system.

If not that, then second favourite is a leak inside the heat exchanger. The expension vessel is only one of the main culprits.
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Thank you both for your answers. I'll put my trust in the Gas Safe man and hope he can identify the cause of the problem.

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Combi Boiler Losing Pressure

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