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Discuss Can't find leak from our ch/boiler, losing a ton of water somewhere! in the Plumbing Forum area at

  1. Kate15

    Kate15 New Member

    Hello, really hoping someone can help .

    We've been losing pressure on our hot water system for about a year now. It worked fine over summer but now winter's kicked in we're having to top up several litres every day to keep the boiler working (it switches itself off after about half an hour use).

    All our pipework is in between the ground and first floor and all the pipes to the downstairs radiators are visible. There's no sign of a leak anywhere in the house.

    We have an ariston 23mffi microcombi which is not losing any water from the pressure outlet valve (it's in a place where I'd be able to tell easily).

    I've had 3 plumbers round and none of them have really been able to figure out the problem I don't think. Two have suggested replacing the boiler - it's 10+ years old or so, it'll probably need replacing soon but obviously I don't want to spend ££££ only to find it hasn't sorted the problem.

    Is there any way this could be caused by a leak within the boiler that's then evaporating off? The volume of water that's being lost should be pretty obvious if it was leaking above our ceiling so we're pretty stumped. If anyone has seen this before please please help!
  2. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Ask one of the engineers to top the pressure up then isolate the heating valves under the boiler and see if the pressure drops on the gauge if it does it is a boiler issue
    • Agree Agree x 1
  3. Last Plumber

    Last Plumber Plumber GSR

    As above. Did none of them make a decision as to whether it was a leak on the Boiler or the system?

    If it's not the Boiler, it could be a leak in a wall maybe, on one of the drops to a rad?

    Have a look at the condensate drain when the Boiler has been off for 5 min, there should be nothing coming out of it.
  4. Kate15

    Kate15 New Member

    Thanks for reply - much appreciated. I don't think the pressure gauge on the boiler is working properly (it's a needle gauge and it seems to stick) - would the engineer be able to attach a gauge of their own or do we need to replace the one on the boiler in order to test it?
    • Winner Winner x 1
  5. Last Plumber

    Last Plumber Plumber GSR

    How do you know where to top up to ?
    If the gauge doesn't work ?
    You may be going too far with it. Get an Engineer to fix the problem and check the Boiler over.

    I would expect in a short visit they would be able to tell you what needs to be done.
    • Agree Agree x 1
  6. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    That’s what I Also meant by saying get it changed.
  7. Kate15

    Kate15 New Member

    I can tell where to top up to because I hear the microswitch flicking and the boiler fires up!

    As I've said, I've had 3 engineers round and so far no joy .

    Where would I find the condensate drain?
  8. Kate15

    Kate15 New Member

    Sounds like new pressure gauge is probably the place to start?
  9. king of pipes

    king of pipes Trusted Plumber GSR

    The expansion vessel needs checking or even replacing and possibly the saftey valve and gauge , a 10 year old boiler its not worth spending more than a few 100 pounds on once you start spending other components will fail. Kop
    • Agree Agree x 2
  10. Last Plumber

    Last Plumber Plumber GSR

    Too true.
    Easy to be tempted but all parts are the same age with the same wear n tear.
    There's many a customer who regretted the 'repair it' decision.
    • Agree Agree x 2
  11. Tim Court

    Tim Court New Member

    I would start with the pressure gauge. If you are filling it till you hear a click it might be only just fractionally within it’s working pressure range. When it has cycled a few times, especially with an old pressure vessel, along with a little bit of air in the odd rad or two, it might just drop the fraction necessary to switch out. Gauge is relatively cheap too!
  12. jtsplumbing

    jtsplumbing Plumber GSR

    This is a standard boiler so no need to worry about the condense pipe, if your loosing pressure with no visible signs of water then its a good chance that the heat exchanger is faulty,
  13. Kate15

    Kate15 New Member

    Many thanks for all the replies. Given that (at least) the pressure gauge has gone and the boiler is getting on a bit I think it probably is time for a new boiler, I've asked a local plumber to quote. Thanks again.
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