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    Why is my boiler losing water pressure?

    Heating Engineers

    Recently had my central heating system updated and the boiler keeps losing pressure. I've checked for leaks and there isnt any under the floors. What else should I be checking?

    Asked by Sarath on 29th Mar 2020
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    Best Answer

    Bjc plumbing & heating

    "If it’s a new system, it could be a number of reasons.
    1, being a leak
    2, expansion vessel has insufficient charge
    3, pressure relief valve is letting by
    4, cracked heat exchanger"

    Answered on 29th Mar 2020 - Member since Feb 2020 - report
    MLB gas heating and plumbing services

    "Depending how old the boiler is it may require a new pressure vessel"

    Answered on 29th Mar 2020 - Member since Jan 2020 - report
    Jt heating &plumbing

    "Possibly a leak, possibly pressure valve or may be the pressure vessel"

    Answered on 29th Mar 2020 - Member since Nov 2019 - report
    Chas Stewart Plumbing & Heating Ltd

    "Could be expansion vessel or pressure relief valve"

    Answered on 29th Mar 2020 - Member since Apr 2017 - report
    Profile Plumbers

    "It’s possibly an issue with the expansion vessel and pressure relief valve letting by or a leak on the heating system"

    Answered on 7th May 2020 - Member since May 2018 - report
    GWE Compliance

    "Hi,
    It's a common problem when converting from a traditional or ' open vented ' system to a modern ' pressurised ' system.
    The leak doesn't necessarily need to be a visible drip, a tiny weep will cause the noticeably drop in a relatively short period of time.
    As the boiler is new I'd be surprised if the issue lay within the appliance itself, you could try adding some leak sealer into the system, like F4, this is designed to safely flow around your system and seal tiny leaks, if the pressure is dropping over night it would suggest you have a larger leak and you have possibly missed it.

    I hope this helps,
    Lee
    GWE Compliance q"

    Answered on 31st Mar 2020 - Member since Mar 2020 - report
    GB’s Plumbing and Heating

    "There could be several reasons. Most probably the expansion vessel. Depending on the boiler it needs checked to ensure it’s charged as per manufacturers instructions.
    The pressure cookers relates only to the heating system. Isolating the flow and return overnight would show if the pressure drop comes from within the boiler as opposed to the rest of the heating system.
    If it’s recently been installed contact the company that installed it."

    Answered on 29th Mar 2020 - Member since Mar 2020 - report
    DGN Gas

    "How recently did you have it updated? Could be still air in the pipes or radiators so as that is leaving the system the water pressure is dropping.

    Did you change the system? ie. was it previously open vented and is now sealed?"

    Answered on 29th Mar 2020 - Member since Mar 2019 - report
    AGS 24/7

    "There are two reasons this can occur, the first and most likely is a water leak. The radiator valves are the first place to check and it only takes the equivalent of a couple of inches of water in bucket for the gauge to read zero. If your radiators have bleed valve plugs that can be replaced and these are sticky brown rather than wet they are the problem. If both of these are ok, look outside at the copper safety valve termination below your flue and if this is wet your safety valve is faulty and will require replacing.

    The second cause is that your expansion vessel is flat and this will require an engineer to recharge it, and it should also be checked if you have a leak and have repaired it."

    Answered on 29th Mar 2020 - Member since Jan 2020 - report
    J M R plumbing and heating

    "If your boiler keeps losing pressure and there are no leaks, it could be the expansion vessel needs changing and possibly the prv."

    Answered on 29th Mar 2020 - Member since Mar 2020 - report
    Hayes plumbing and heating services

    "Because you more than likely have a leak on you heating system. Check all radiators"

    Answered on 29th Mar 2020 - Member since Apr 2019 - report
    Elsey & Co Ltd

    "Hello Sarah. It could be a depressurised or faulty expansion vessel along with the pressure release valve letting by.
    Thanks Andy"

    Answered on 29th Mar 2020 - Member since Feb 2017 - report
    MS Heating & Plumbing

    "If you have any pipes chased in on a ground floor, I've had leaks on pipes chased in the ground which you cant see.
    Other than leaks it can only be your expansion vessle or prv on the boiler."

    Answered on 29th Mar 2020 - Member since Dec 2019 - report
    Lehaps Gas

    "If the boiler is losing pressure, the pressure relief valve and expansion vessel requires attention."

    Answered on 29th Mar 2020 - Member since Dec 2018 - report
    GHF/PPH

    "Hi,

    Normally the reason why your boiler is loosing pressure is due to there being either a leak or an opening on your system."

    Answered on 29th Mar 2020 - Member since Jan 2020 - report
    Ryedale Plumbing Services

    "Hi. If it’s recently been updated and you’re still lossing pressure I would be reasonably confident that you have a leak somewhere. Have you checked under floors and/or loft etc? It’s unlikely to be in the new boiler, but it would be sensible to get your installer back to check the system. Hope this helps. Thanks.
    Richard"

    Answered on 29th Mar 2020 - Member since Mar 2020 - report
    JS plumbing and heating

    "You may need the expansion vessel looked at. I'd call back the tradesperson who installed the boiler to check it.

    Joseph."

    Answered on 29th Mar 2020 - Member since Apr 2019 - report
    Mark Oliver Plumbing and Heating

    "You need a qualified heating engineer to look at the boiler.

    There are various safety mechanisms on the boiler that may need looking at.

    If it's gas fired; A Gas safe engineer
    If it's Oil fired; An Oftec registered Oil boiler technician

    Check their Identification cards when they attend to make sure they are and their qualified to work on your boiler."

    Answered on 31st Mar 2020 - Member since May 2018 - report

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