losing pressure...ongoing.

Discussion in 'Plumbers' Talk' started by jimbobby, Sep 19, 2021.

  1. jimbobby

    jimbobby Active Member

    HI
    Update.
    WB boiler. 6 years old...10 rads . System 20 years old. No signs of leaks on any rad...checked carefully.
    losing pressure when CH used...
    Can set to 1bar and no loss over seven days if CH not used.
    Pressure loss to zero over 3 days when CH used.
    Recent WB engineer out.
    Replaced air vent, new PRV guts. pressurised EV...no water in it.(previous engineer found lots of condensation in it ?????)
    New schrader valve.
    Any ideas ?

    cheers
    J
     
  2. Wayners

    Wayners Screwfix Select

    Im not a plumber.

    Crack in heat exchanger in ours causing pressure loss with no signs of water leak. Just evaporates inside I guess.
     
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  3. exbg

    exbg Active Member

    No, it escapes via condense pipe
     
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  4. Wayners

    Wayners Screwfix Select

    Guess that explains it then. Out the condensing pipe.
     
  5. terrymac

    terrymac Screwfix Select

    If the heat exchanger is pin holed ,I would expect pressure loss even when central heating is not used ,over 3 days.
    Of course it's possible that when heating is on the expansion makes a difference ,but I am more inclined to think it's a leak on the system.
    Is the PRV pipework dry ?
     
  6. exbg

    exbg Active Member

    Turn off flow and return valves below boiler. If HEX is pinholes, the pressure will drop VERY quickly
     
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  7. pppmacca43

    pppmacca43 Super Member

    Have u tried putting a bottle of leak sealer in the system, Never used it before myself but it’s apparently very good stuff. I’m sure someone else who has used it can confirm if it’s worth a try.
     
  8. jimbobby

    jimbobby Active Member

    Used leak sealer.
    WB guy says he can confirm its not the HEX as he pressurised the boiler in the attic and it held pressure.
    (realise that heating will cause expansion etc)
    First WB guy said condensation in EV...how can it be condensation? from where ?
    Cover runs out next year so need to get it sorted by WB.

    No apparent PRV problem as it was replaced.
    Pressure does not drop off gradually , its on 1 bar during evening and on zero next morning ( after about 4 uses)
    thanks
    j
     
  9. terrymac

    terrymac Screwfix Select

    That's not quite what you originally told us in your first post ,is it getting worse now it drops to zero overnight ? With 4 uses ??? What does that mean ,after domestic hot tap water has been used 4 times ? I assume it's a Combi boiler.
     
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  10. jimbobby

    jimbobby Active Member

    WB combi. 6 years old.
    Checked every year.
    Previous problem was dropping to zero overnight.
    WB guy out.
    Says EV full of condensation..(how? can anyone explain this)
    Better for a few days and then started to drop but not every time when CH used.
    New WB guy out recently.
    Parts changed as mentioned.
    Ok for a week with CH use 3 or 4 times for maybe 40 mins at a time.
    Dropped to zero...topped up. Ok for a few uses of CH then dropped.
    CH pressure does not drop slowly or at all when not used and set to 1 bar.
    j
     
  11. exbg

    exbg Active Member

    Re pressurising boiler in loft: what exactly did he do?
    It may be that the a pinhole in HEX expands when heating on.
    If you isolate F&R under the boiler, the massively reduced water content very quickly shows a pressure loss. If this test shows no response then you are left with expansion vessel issue or PRV failure.
    Tue a ballon or disposable glove to PRV outlet to prove no passing.
    If neither test shows an indication, and no water collecting within case, the problem is a leak in the system
     
  12. ElecCEng

    ElecCEng Screwfix Select

    When you checked the rads carefully did you isolate them all with the lockshields and test the system?
     
  13. jimbobby

    jimbobby Active Member

    No...just looked for signs of leaks at valves.
    Do you think it might a rad leak ?
    j
     
  14. ElecCEng

    ElecCEng Screwfix Select

    Just that it’s worth ruling out. Relative had a repeated pressure loss (admittedly slower than yours) and eventually identified a pinhole in a rad.

     
  15. jimbobby

    jimbobby Active Member

    Thanks...open to all possibilities.
    j
     
  16. DaveF

    DaveF Active Member

    One thing I would check is do you have a double valve on the filling point? It could be the valve is leaking water back in to the cold water supply when the pressure rises above mains pressure.
     
  17. Mike83

    Mike83 Screwfix Select

    You need to go back to the beginning.
    If it’s a combi fill to 2 bar. 2 bar is high but better for this test.
    Then close both F&R isolation valves.
    Use hot water as normal for 3 days or so. This is perfectly safe to do.
    Then take note of the water pressure. If it’s still 2 bar then open the isolation valves.
    If the pressure immediately drops then it’s on the heating circuit.
    If the pressure is below 2 bar with the valves closed then it could be a boiler issue.

    The above test needs to be done if there’s no visible water leaks.
     
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