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Slow boiler pressure drop

The boiler is dropping pressure slowly over a period of a few days, radiators have been bled and valves checked with no sign of leaks. Is there a way to try and trace the cause? I considered a specialist leak detection firm, but they have said that if the leak is too slow i.e. less than a bar over 24 hours their equipment won't be able to trace it. The system was only installed a few months go, we were advised by contractor at the time that all was good to go so slate flooring has since been laid and access is now limited. The boiler has been completely checked by an independent gas engineer and all good. Is there anything I can set up to try and understand where the problem may be ?

Thank you for the suggestions. I think I will get ask the contractor to check the boiler - pressure relief valve & expansion vessel for damage. Also, concerned that the warranty they will hand me may not be valid if these items are not checked.

3 Answers from MyBuilder Plumbers

Best Answer

Hi, if the leak is so small to detect then try using a bottle of Sentinel leak sealer or something similar that you add to your system and should hopefully seal. Screwfix sell for £15.99.
Kind regards


Answered 2nd Oct 2020

If the pressure is dropping on the boiler, there is obviously a leak some where in the system.

I would suggest you call the contractor back to check the whole system again!
There are products on the market that you can to the system to seal very small leaks. The question is “why should you have resort to this with a new heating system????)


Answered 2nd Oct 2020

Hi . It could be your pressure relief valve . Check that first . It usually is a pipe that goes to outside ( a bit like an overflow) I might be slowly dripping


Answered 29th Oct 2020

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