Topping up pressure every couple of hours

Discussion in 'Plumbers' Talk' started by Hunter7777, Feb 2, 2021.

  1. Hunter7777

    Hunter7777 New Member

    Hi everyone,

    I would really appreciate any advice or ideas anyone has for our ongoing situation which none of the tradesmen so far can figure out.

    When our central heating is on we are losing pressure every couple of hours (starting at 1.5 bar and drops to 0). We then have to top this up via the filling loop. This has been going on for a number of years!

    We have had the boiler replaced, a new pressure vessel, we have had said pressure vessel re pressurised recently, we’ve had a plumber confirm no leaks in the oil fired boiler, a plumber confirm the PRV is not leaking, we had (a very expensive) visit from a leak specialist company recently who used a matter of investigative machines etc but could not find a leak and their recommendation is to just leave it until there is evidence of a leak in the future. They also said about getting a larger pressure vessel to help - but surely this makes no sense?! There is no visible leaks anywhere on any floors, ceilings or rads. We’ve had a plumber bleed air out the system, check our water pressure tank (mega flow) that we also have but all seems fine with that.

    We really want to get to the bottom of this as just leaving it until there are signs of a leak is bad advice in my opinion considering this has been going on for years with no signs already. We had new flooring end of 2019 where all concrete was on show and there were no signs anywhere.

    Help please as we are at our wits end!

    Thanks

    Rach
     
  2. terrymac

    terrymac Screwfix Select

    Does pressure drop when central heating is not running ?
    Surely it hasn't been losing pressure every day for years ?
    When was the system ok watertight / not losing pressure exactly ,and for how long was it ok ?
     
    Hunter7777 likes this.
  3. Hunter7777

    Hunter7777 New Member

    So we have done the test of having the central heating off for 6 hours and monitoring the pressure. It only dropped 0.2 bars and we were told that could be from if the pipes weren’t completely cool when testing began or if we happened to have washed our hands in that time for example.

    It’s been at least 4 years (doesn’t effect us in the summer as not using the heating) this has been happening. Seems to be worse since the pressure vessel was repressured a couple of months ago but even before that it was at least twice a day top up.
     
  4. terrymac

    terrymac Screwfix Select

    If you have central heating pipes buried ,it's highly likely there is a leak on them
     
  5. Hunter7777

    Hunter7777 New Member

    We do have pipes under concrete on ground floor but the leak specialist used a tracer gas, thermal
    Imaging and acoustic tests and couldn’t locate a leak anywhere. They said they believe it must be when heating is on it causes the hole to open, which is why it only loses pressure when it’s on. Does this sound right?!

    A few years ago we had a leak on the ground floor but this was found due to damp up the wall, there isn’t any signs anywhere at present. So I need some more ideas of what to try if possible as just leaving it to get worse can’t be the only option...
     
  6. terrymac

    terrymac Screwfix Select

    You could consider re routing Pipework above ground ,and make the underground stuff redundant.
    Could be expansion when heating is on exacerbates the leak . These " specialised leak detection company's" are not always successful ,and why they didn't do any testing with heating on is rather odd.
     
  7. Mike83

    Mike83 Screwfix Select

    Maybe not a job for just now but if you can locate the flow and return pipes for downstairs and isolate them before going under the floor.
    This would ensure the upstairs and hot water still work.
    With the downstairs isolated from the system use the system as normal.
    If the pressure no longer drops its under the solid floor.
     
  8. fred812

    fred812 Active Member

    My guess. You've got a nail or screw penetrating a pipe. When cold it effectively seals the pipe, when hot it expands and moves slightly. I'd be looking at pipe runs in the floor where this could be the case.
     
    Creek likes this.

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