Boiler losing pressure when running

2 Dec 2005
Reaction score
United Kingdom

My boiler losers pressure over a day even when the heating is running, I know that my valve in my expansion vessel is leaking.Guessing thats the cause..Its an Heatline c24 is it possible to change the whole valve or get a tool that removes the middle part and replace..Thanks for any advice.
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Thanks for your response..Is this to replace whole valve or just internal part?

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I now have the removal tool and new replacement valve..Do i need to turn off boiler and drain to replace??Thanks
At least depressurise system(water side) if your diaphragms gone you'll get a shower!
is it leaking air or water from the valve? (im going to assume its water as thats more common) if thats the case then replacing the valve will only be a short term fix, the membrane in the expansion vessel has failed and water has entered into the air only section. Your need to either replace the expansion vessel or add a second one to the return line on your system.

If it just air thats leaking, bonus!
It only seems to be air but I have brought the valve removal tool but valve doesnt seem to undo..I am think of putting an external expansion vessel next to the boiler..If I disconnect the braided hose from the bottom of the exsisting expansion tank and run this out the side of the boiler and connect to the new external one will that be OK??Also I have a total of 7 radiators and the external vessels seem to state that per litre size is equal to number of rads..IE 8 litre will cover 8 rads..Should I go for the 8 or the 12..Not much in the price.Thanks in advance

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