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Valiant combo pressure keeps rising

Discussion in 'Plumbing and Central Heating' started by jp butterworth, 30 Jan 2016.

  1. jp butterworth

    jp butterworth

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    Hi

    The pressure goes up gradually overall and have to bleed every 3 days or so. It goes up when heating is on and down when not but overall it keeps rising. I disconnected the filling loop.

    - it's a gas combi about 4 yrs old
    - I tried to get a non working rad working by bleedin it then turning off other rads to get pressure to it(first time this had been done in 4 yrs)
    - got a leak from another rad so had to re pressure (first Tim I've done this)
    - then the prob started.

    What are the usual suspects here anyone? Could the heat out flow be a bit blocked? I know people talk about the hot water part of the boiler system leaking into the heating, but Seeing ask was mucking around with pressuring/bleeding for the first time I guess I'm thinking this my have caused somet.

    Any advice appreciated!
     
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  3. nortonj

    nortonj

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    Sounds like you have sn expansion problem. The rad full of air was masking this problem. Search the frequently asked questions it will be under expansion vessel.
     
  4. Aquaheat

    Aquaheat

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    If the filling loop has been disconnected turn off boiler and isolate mains cold water into the boiler. See if this stops the pressure rise.

    Jon
     
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  5. jp butterworth

    jp butterworth

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    Thanks guys. I will try your idea Jon when I get in.

    I don't understand how a faulty expansion vessel would make the system pressure rise gradually over days. Wouldn't it just be that the pressure would rise much more when heating was on but fall back down when cold?
     
  6. simond

    simond

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  7. nortonj

    nortonj

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    You did say
    but you may have two issues. Try Jon 's suggestion then look at expansion.
     
  8. jp butterworth

    jp butterworth

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    The is a small leak in the valve on the filling loop at the heating return end but the end of the loop at the mains is fine so I can't imagine this is an issue?

    Having heating AND water off for a couple of days is not fun with a 1 and 3 yr old in the house! When u say to isolate mains cold Jon should shut the valve lets it in to the boiler?
     
  9. Aquaheat

    Aquaheat

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    Yes there is a cold main entering the boiler on 15mm pipework. Usually the second pipe in from right or left.

    It may not be fun but you should notice a rise in a day or so at your rate and will lead you to the fault. Maybe turn off in a morning and check when you return of an evening. Mark the gauge so that a rise is easily noticed.

    Jon
     
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  11. jp butterworth

    jp butterworth

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    Ok thanks Jon Ill turn off the mains valve and boiler and report back.
     
  12. Aquaheat

    Aquaheat

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    Sorry for the delay @jp butterworth

    If you could do that it would be great as it will give us a better idea of whats happening. Taking into account temperature increase during the day you should still be able to tell if it is rising over a period. When you turn off the mains let us know what it is sitting at and do try to leave it at least 12 hours if is just a small leak and then let us know what happens.

    The next step would be to isolate the boiler from the system so that we could pin point a side and know where to look from there.

    Might be a silly question but are you sure you have a combi. Sorry if it seems a silly question but some people do confuse systems.

    Jon
     
  13. jp butterworth

    jp butterworth

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    Hi Jon found a slot to turn off for 24hrs. The pressure didn't rise with the boiler switched off and cold mains off also. Its a valliant 831.

    Wife and I are arguing over whether or not the trickling sound from boiler that lasts about 3 seconds when heating is on (or maybe water e.g Dishwasher) is heard more frequently now (every few mins). We can't remember...
     
  14. muggles

    muggles

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    If the pressure rises when the cold inlet valve is on, but doesn't rise when the valve is off, and you're sure the filing loop isn't passing, you have a failed heat exchanger which will need replacing
     
  15. Aquaheat

    Aquaheat

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    As muggles says, and why we asked yiu to do that test, if you are sure that the filling loop is disconnected then I'm afraid you have a faulty DHW Hex.

    Best thing is to get an engineer out and mentioned your suspicions and tell him what tests you did. Give him chance to test himself and confirm diagnosis and what it will cost to repair.

    Jon
     
  16. Aquaheat

    Aquaheat

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    Also if you put in a location in your profile or post the start of your postcode then there may be one of us engineers on here close to you that could help you out.

    Jon
     
  17. jp butterworth

    jp butterworth

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    Thanks guys. Why do you think this failed ? It must have been something I did as it was fine for 4 yrs then I did what I said at the start of this thread... And when u say failed, it's a leak right?

    Roughly what do u think total price would b if this is the prob?

    Cheers
     
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