pressure dropping in central heating

Discussion in 'Home energy' started by Tebbit, Mar 12, 2018.

  1. Tebbit

    Tebbit Frequent Poster

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    How often should you have to top up the pressure on the central heating by opening the pressure valve to let in more water? or should you have to do it at all?

    the pressure on my system over 15 months has gone from 1.3 to 0.6 - any comments on this. 15 months ago I had sealant put in and before that I would have needed to top up much more regularly.
    thanks
     
  2. Seagull

    Seagull Frequent Poster

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    That drop over 15 months is perfectly acceptable. It's when it's happening overnight that you get concerned. I'd expect to be topping up slightly at least every 2 or 3 months.
     
  3. theresa1

    theresa1 Frequent Poster

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    Maybe top up once every 12 months -every 2 or 3 months is too much -ask any Plumber.
     
  4. Tebbit

    Tebbit Frequent Poster

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    Thanks for that . Feel better after hearing it. Would it be when it gets to 0.5 that you'd top up ?????
     
  5. Seagull

    Seagull Frequent Poster

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    I wouldn't be too fussed about topping up at a particular point. Just don't let it get too low. Is that the hot or cold pressure you're giving? What is the recommended operating pressure for your system? Our boiler manual had 1.5 to 2.

    I don't typically put in a huge amount. The plumbing in our estate leaves much to be desired. There were 3 potentially dangerous breaches of regulations that we've found so far in the heating system in our house.
     
  6. roker

    roker Frequent Poster

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    Can I add a question here about a pressurised system, why is the the top up valve kept closed? Would it not be better to leave it open and allow the pressure regulator to constantly keep it topped up?
     
  7. Leo

    Leo Moderator

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    If the top up valve is open, the increased pressure as the water heats will force inhibitor laded system water back out of the system. As it cools, it'll draw more air carrying cold water in causing further issues with air locks and corrosion.

    If you find yourself constantly needing to top the system up, you have a leak.
     
  8. rob oyle

    rob oyle Frequent Poster

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    I assume that, if the reverse occurred (mains pressure reduces through leak or cut off through weather etc.), you wouldn't want the closed system pushing water back into the fresh water system... who knows where that's been!
     
  9. roker

    roker Frequent Poster

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    This would not happen because there is a check valve stopping it go back
     
  10. Leo

    Leo Moderator

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    When there's enough of a pressure differential to operate the check valve that is. If there isn't enough of a differential to force the seal, or there's equal pressure on the heating side of the check valve you will still have inhibitor migrating beyond the valve diluting the system water.