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Boiler Saga Continues - Probable Leak...(Update 24/12/20 - Trace and Access visit)

Discussion in 'Plumbing and Central Heating' started by siross85, 8 Dec 2020.

  1. siross85

    siross85

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    Hi all,

    Apologies in advance for the long thread, I'm trying not to go insane! I'm fairly sure there's a leak somewhere but before I shell out I just want to make sure it's not something simple and/or obvious that I can check myself...

    I'm having some problems with the pressure dropping on my boiler, this is an ongoing saga! As a bit of a back story, we moved in to the house 18 months ago and had some work done to make an open plan area which meant a radiator was removed and capped off and a larger radiator installed.

    After this we had issues with the boiler, the plumber used some leak sealer which was not effective. The plumber looked for the most likely culprit and found a leak in the capped off radiator, they did this by knocking a couple of bricks out, getting their hands in and fixing before refitting an air brick. All was well for a while.

    During the past couple of months the problem of losing pressure has returned, we have British Gas Homecare included with our gas contract so I've called them out after checking all radiators and not seeing any signs of any leaks.

    The pressure was actually rising when the heating was on before then dropping to zero over a few hours. This was immediately diagnosed as the expansion vessel which the engineer then charged up. This did not solve the problem. The engineer came back, fettled with the expansion vessel again and cleaned everything, including the Mag Filter attached to the boiler. Again no solution.

    During all of this the heating and hot water was working fine. The only noticeable issue was air getting in to the radiators upstairs and causing noise. I was having to bleed the radiators every other day. Bleeding them often took a long time as a lot of air was in them!

    When the plumber was investigating the issue 18 months ago he installed some isolation valves on the pipework which effectively isolated the downstairs heating pipes. I've isolated the downstairs using these valves and the pressure was fine, this would obviously point towards the culprit being a leak somewhere in the system.

    I've had the same air brick out from last time and had an inspection camera in there, I can see quite far under the kitchen floor and a number of joints. There are no signs of leaks or dampness anywhere, it's very dusty and dry and no water coming out. However that doesn't mean there isn't a leak somewhere else on the downstairs system.

    The British Gas engineer came back and used the leak sealer again to see whether it would help, it didn't. The boiler is losing pressure quicker than before, it's going down to zero in an hour or so. However, it did seem to temporarily stop air getting in the system, however I'm back to bleeding the radiators every other day. I have to top the system up twice to get the air out!

    I've topped up the system and isolated the downstairs heating pipes again as a double check and the pressure stays constant over an hour or so, testing the heating going on and off. The pressure climbs from 1.2 to 1.5 and stays constant when heating on, drops back to 1.2 when heating off. When I've opened the isolation valves again the heating comes on and the pressure rises to 1.2ish and stays there. Once the heating has gone off, the pressure drops back down to 0 after an hour.

    All this leads me to think there's a leak under the floor and I'll have to get a specialist trace and access company to find it (there's no crawl space). But I can't get my head around the following:

    - The boiler still works as normal, besides air in the rads causing them to make noise and rattle.
    - The boiler pressure will remain constant if the heating is on. It was explained to me that this will be due to the pipes being hot and expanding which may be stopping the leak. However there is no delay in this, if I were to put the pressure to 1.5 bar now when it was cold then turned the heating on, it would stay at 1.5, it wouldn't drop until it warmed enough to expand?
    - Even after the pressure has reached 0 when the heating is off, the pressure will actually climb slightly, I've seen it go as far as 0.5bar from zero after the heating has been on for an hour or so? Surely the pressure would just continue dropping as it is losing water from a leak?

    Is there anything else I can do to check before shelling out for a trace and access company?

    Cheers,

    Simon
     
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  3. CBW

    CBW

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    If you’ve seen the pressure rise, then you could have a split secondary heat exchanger or a passing filling loop if connected. Have you checked the pressure relief valve pipe outside?
     
  4. Harry Bloomfield

    Harry Bloomfield

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    Put a plastic sandwich bag over the end of the pressure relief valve, with an elastic band to seal it on the pipe. If the PRV is passing, water will appear in the bag.
     
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  5. siross85

    siross85

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    I don't have a pressure relief pipe outside. The relief and condensing pipe are one in the same unfortunately which goes straight in to a drain outside via black flexi pipe. I've had this pipe out and in a bucket, when the heating is turned on quite a bit of water comes out initially then not much after that.

    Apologies for the daft question but presumably that means opening up the boiler? I've not done that before. Happy to give it a go though
     
  6. Harry Bloomfield

    Harry Bloomfield

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    It is a 15mm pipe, which normally pokes out through a wall, ending in an elbow pointing towards the wall. Usually it will be close to where your boiler is mounted. Idea is that if pressure builds up too high, the PRV opens and releases the excess pressure outside. Sometimes they leak when they shouldn't and the way to check, is by fitting a bag over the pipe end to see if it collects any water.
     
  7. CBW

    CBW

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    He’s just confirmed it’s combined with condensate pipe
     
  8. CBW

    CBW

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    What boiler is it? You could try raising the pressure to approx 2.8 bar, and see if anything noticeable appears on rads. Have you checked the filling loop?
     
  9. Harry Bloomfield

    Harry Bloomfield

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    Then the OP sounded confused about accessing the PRV outlet, talking about opening the boiler up.
     
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  11. CBW

    CBW

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    @Harry Bloomfield, I think OP needs to post a photo of combined prv/condensate to clarify then
     
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  12. siross85

    siross85

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    It's an Intergas Rapid 32, I've been told by various engineers that it's a weird boiler. It was installed by previous owners. When you say check anything noticeable on rads you mean leaking/and bubbling? I've not checked the filling loop, what would that involve? Technically I haven't checked the boiler at all, only the gas engineers have.

    Apologies for confusion I thought the PRV being referred to was an actual valve in the boiler, not the pipe going outside. The PRV and condensate pipe are the same thing.

    The pipe looks like this: https://www.screwfix.com/p/tower-co...0mpgEVLZreQdXsEvah0aAoTREALw_wcB&gclsrc=aw.ds
     
  13. CBW

    CBW

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    I doubt it’s combined, unless you have a tundish. Yes I mean leaking radiator valves. If the filling loop is connected, then a simple disconnection should confirm this.
     
  14. Tally101

    Tally101

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    I had a simular problem for years where the boiler would lose pressure over night and spent hundreds swapping things to try to fix it eventually we found it when the kitchen was been renewed and a wall taken down we had the ceiling down and I found a connection dripping and just needed nipping up. fingers crossed its fixed :)
     
  15. siross85

    siross85

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    I'll take some pictures tomorrow if that would help? It was the gas engineer that said it was a combined system.

    When you say filling loop do you mean the loop used to top up the boiler with water to increase the pressure? What do you mean by disconnecting the loop?

    Thanks, I'm hoping it's sorted soon. I'm losing sleep over it now!
     
  16. Gasguru

    Gasguru

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    Intergas are some of the simplest boilers ever made...anyone who has trouble understanding them should be shown the door.
    It has a combined PRV and condensate outlet.
    These boilers can be run as a hot water only or heating only boiler with the unused circuit drained.

    When water is heated it expands...so with the heating on you'll see a few percent increase in volume hence the modest pressure rise....this is common to all sealed presurised systems.
    When the system cools the pressure drops back.
    Leaks on the system often cause air to become trapped in radiators (despite being a presurised system).
    You've proven where the leak is so sort out the downstairs pipework and job done.
     
  17. siross85

    siross85

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    Hi, thanks for the reply. Didn't realise they were so simple. I tried to get Hive installed and the BG engineer literally refused to install it because it wasn't in his list of boilers with instructions!

    So would you say the boiler is definitely not the issue?

    Problem I have is finding the leak without a crawl space and all floors are laminate and tile. If it's 100% a leak then I'll be best shelling out for the trace and access experts to come in.
     
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