Boiler help

Discussion in 'Engineers' Talk' started by Kelso3, Sep 16, 2017.

  1. Kelso3

    Kelso3 New Member

    Hi just looking advice. The pressure on my boiler drops everyday to zero for weeks. Had gas engineer out who serviced the boiler replaced parts etc. He said if the pressure still dropped after this then there was a leak in the house.
    So next day the pressure is zero again. I get a plumber out who checked the house and says there is no leaks in house.
    When he went outside he said there is a constant drip coming from the waste pipes when he tracked it, it's coming from the boiler.
    When I asked the gas engineer about this he said that it
    was normal its condensation. But its not once in a while it's a constant drip directly from the boiler.

    Any ideas what I should do now?
     
  2. Hi Kelso.

    What make and model of boiler?

    I presume it's a modern, High-Efficiency condensing type? Combi or system (do you have a hot cylinder)?

    Ok, if a system loses pressure, it's either from within the boiler or it's from the rest of the system - the rads and pipes, etc. The way to test for this is to isolate the boiler from the rest of the system by turning the two valves located on the 22mm 'flow' and 'return' pipes under the boiler. If you get your system up to 1 bar pressure and then shut off these valves AND ALSO SHUT OFF THE BOILER!, then - if the pressure still drops - the leak is from within the boiler.

    How can water escape from the boiler without leaving a puddle on the floor? Via one of two pipes. One is 15mm and copper, and this is the safety discharge pipe. It ends up outside the house, and should be pointing down at the ground or back on itself against the wall (the pipe is curved in this case). This pipe should not have any water coming out of it - it's only there as a safety measure to release excessive pressure if your system goes wrong.

    (But, it would be good news if it is this pipe, 'cos the repair is likely to be cheaper... A faulty PRV valve, and possibly the exp vessel needs a top-up)

    The other pipe - the condensate drain - is 22mm dia and plastic. This pipe will have 'water' (slightly acidic condensate) coming out of it when the boiler is running. The water comes out in 'glugs' every few minutes during this time. When the boiler is off, however, the glugs should stop and there should be no more drips after, ooh, a half-hour or so.

    If this pipe is continuously dripping, tho', then that suggests a significant issue - a leaking main heat exchanger. This will almost certainly cost £100s for a replacement.

    (But, depending on model, you may have a claim.)

    So - is the water coming out the thin copper pipe or the larger plastic one?
     
    KIAB likes this.
  3. KIAB

    KIAB Super Member

    And age of boiler.
     
  4. Kelso3

    Kelso3 New Member

    Thanks for all information. It's a vokera compact 24. Not sure the exact age it was here when I brought the house and I've been here 3 years. The drips are coming from the white plastic pipe from the boiler
     
  5. If it continues to drip when the boiler offski and cold, that's not good.

    Place a jar under the pipe, repressurise the boiler to, ooh, 1 to 1.5bar, leave it turned off for as long as possible and monitor what comes out.

    When the boiler is actively running your CH, it will produce glugs of water every few minutes out that pipe, but this should not happen when it's off.

    The amount of water required to get your pressure back up from an indicated zero to 1 bar is around - very roughly - a cupful. Or two. Roughly...
     
  6. Bob Rathbone

    Bob Rathbone Screwfix Select

    I would put a container under the drip to collect and measure the water loss. System venting will be due to many factors, but commonly try these 2.
    1/ The pressure relief valve is leaking by. Solution, fit new.
    2/ The expansion vessel on the boiler is not large enough for your system or has not been pressurized correctly. Solution, check pressure in expansion vessel, if OK fit additional expansion vessel somewhere on the system.
     
  7. KIAB

    KIAB Super Member

    Vokera horrible boiler, a friend had so much grief with one, she replaced it with a Valiant.
     
  8. Kelso3

    Kelso3 New Member

    Thanks for all the help guys will let you know the outcome
     
  9. I think we are looking at the plastic condensate pipe, in which case it's likely to be a leaking main exchanger.

    That would usually render the boiler not worth repairing - you are looking at many £100's.

    Unless the boiler is, say, less than 5 years old. Or possibly even older.

    These items simply should not fail that quickly, so you can very likely claim it was of not satisfactory quality from new - or whatever the term is.

    Try a surf for that model and see if it's a commonish problem - that will help.

    (But, of course, we don't know what the actual fault is yet...)
     
    KIAB likes this.
  10. Mike83

    Mike83 Screwfix Select

    Compact 24 is a standard efficiency boiler. The pump housing or the expansion tube between the housing and vessel could be blocked. This would then lift the prv during operation.
    A couple of pictures will help.
     
  11. Kelso3

    Kelso3 New Member

    Pictures not uploading will try again later, but have turned the boiler off and disconnected the white pipe from the drain pipe to monitor how much water comes from it after the boiler is off with a measuring jug underneath
     
  12. Kelso3

    Kelso3 New Member

     
  13. Photos need to be less than 2MP in size.

    Set your camera to a low resolution, or use on-line software to reduce the file size.

    Or try opening the photos using 'Office' (right-click on the photo and chose MS Office from the 'Open with' menu. Once loaded, select 'Picture' > 'Resize' and click 'Predefined width & height' with the default 'document large' usually being fine. 'Ok' and 'save'.
     
  14. Kelso3

    Kelso3 New Member

    I left the boiler off for three hours and the jug was filled to 30ml from the condensation pipe
     
  15. And what did the pressure do during this time? Had you topped it back up? And has it now fallen again?

    How long does it usually take to drop from 1 bar to zero?

    If you can keep the boiler off for another couple of hours, the thing to try is to empty the jug, replace it, repressurise the boiler to 1.5 bar and see what happens with the jug and pressure over a couple of more hours with it switched off.
     
  16. Kelso3

    Kelso3 New Member

    So was at zero I topped it up till one, after 3hours was at 0.8 and 30ml in the jug. Back zero this morning so have done the daily top up. I put the pressure at 1.5 everyday and it's at zero the next morning
     
  17. Bob Rathbone

    Bob Rathbone Screwfix Select

    Only 30Ml in condensate over 3 hours is not much, I would assume that the main heat exchanger is not leaking otherwise the jug would be full to overflowing. What is the safety vent pipe output? that should be very little or nothing.
     
  18. As I understand it, that was with the boiler cold, and with a pressure drop of only 0.2bar (from 1 bar to 0.8 bar).

    In which case the main suspect must be the heat exchanger. In which case - unless you can oblige Vokera to cover the cost - it's a non cost-effective repair.

    Kelso, did you keep the jug in place overnight, or did you reconnect the pipe when you fired up the boiler?

    Another way to test where the leak is coming from is to re-pressurise as before and then close off the isolating valves under the boiler that lead to the 22mm CH Flow and Return pipes. The boiler must be switched off and not turned on during this test.

    Closing these valves effectively isolates the radiators and pipework from the boiler, so if the pressure still falls then it's not from the rads/pipes but from inside the boiler itself.

    Find the serial number of the boiler and ask Vokera what build date that refers to. If it's less than - ooh - 8 years old then I reckon you can oblige them to fix it (invoke the Consumer Rights Act).
     

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