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Discuss Pressure drop after cleaning filter in the Central Heating Forum area at

  1. Spindle

    Spindle New Member

    I cleaned out the magnetic filter on my Worcester boiler for the first time and the pressure has dropped from about 1.7 bar to 1 bar. What could the reason be?
  2. CBW1982

    CBW1982 GSR

    Seems to me like you’ve possibly lost some water from cleaning your filter.
  3. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Did you repressurise afterwards?
    • Like Like x 1
  4. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Also 1.7. Too high
    • Agree Agree x 2
  5. Rob Foster

    Rob Foster Top Contributor!!

    Repressurise you system to 1.5 bar when more. Well done for cleaning out the filter most people dont bother and block their boiler up
    • Disagree Disagree x 1
  6. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Ignore above ^^^^^^

    One bar
    • Like Like x 2
    • Agree Agree x 1
    • Useful Useful x 1
  7. sammathias

    sammathias Plumber GSR

    I'd personally say 1.5bar.
    • Useful Useful x 1
  8. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    I always say between 1-1.5
    • Agree Agree x 4
    • Useful Useful x 1
  9. Coby kenny AGUILAR

    Coby kenny AGUILAR Member

    You've cleaned the filter out whilst the boiler had been running, which is not a problem.

    Sealed systems sit from 1 - 1.5 bar as per manufacturer.

    When the system gets hot the pressure rises for example 1 bar to 1.7 bar.

    When you have a day off, let the system cool and check the pressure then, make sure it's around the 1 - 1.5 bar mark, I personally keep it just over 1 bar as any tiny amount of excess air may vent out of an AAV and pull it below 1 bar.
    • Like Like x 1
  10. Rubin

    Rubin New Member

    If you fill to 1.5 bar when cold when the heating circuit heats up it will be sitting around 2 bar, uneccsssary strain on all Pipework and joints. Better to fill to 1 bar so it’s around 1.5 when hot.
    • Agree Agree x 1
  11. Coby kenny AGUILAR

    Coby kenny AGUILAR Member

    I can see where your coming from but if your sealed system can't take 2 bar when hot, I'd suggest leaving a umbrella for when the diaphragm eventually perishes inside the expansion vessel
    • Funny Funny x 2
    • Like Like x 1
  12. Rubin

    Rubin New Member

    • Winner Winner x 1
  13. Coby kenny AGUILAR

    Coby kenny AGUILAR Member

    Lol I know that's why I said I can see where your coming from.

    There's no right or wrong way if your between 1 - 1.5 but we all have our opinions and none of us are wrong
    • Like Like x 1
    • Agree Agree x 1
  14. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    1.5 bar from cold , why ???????? When any boiler works on 1 .
    • Like Like x 1
  15. John.g

    John.g Active Member

    The expansion vessel pre pressure is a very important setting as well, some are set at 1 bar and if the filling pressure is then 1.5 bar there will be a few litres of water reserve in the vessel while cold to make up any air venting and tiny leaks over time without the need for constant topping up, the pressure will then have to fall from 1.5 to 1.0 bar before this reserve is exhausted. If filling pressure is set to the same value as the pre pressure then this is not possible.
    In general, I would suggest that the filling pressure should be 0.3/0.5 bar higher than the pre pressure.
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