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Intermittent drip & pressure loss Worcester Bosch 28i Ju

Discussion in 'Plumbing and Central Heating' started by DanH, 28 Dec 2009.

  1. DanH

    DanH

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    Hi,

    My girlfriend has just moved into a property with a 5 year old Worcester Bosch 28i Junior.

    I noticed that the pressure was well below the red marker set at 1.5 bar so I filled it up. I noticed that when I topped it up it started dripping slowly from underneath the boiler. This eventually subsided after about 5 minutes so I though everything was ok.

    However, it keeps losing pressure to the point the warning light comes on whereupon I have to top it up again. This happens after a couple of days use or sometimes longer i.e. it's not consistently losing pressure.

    Having read a couple of threads on this I've checked to make sure there is no water coming from the pressure relief outlet which there is none but I haven't been able to watch it for 24 hours. Currently got a dry rag underneath and constantly checking to see if it's getting wet!

    Yesterday, when I had to top it up again I noticed it was leaking a lot more than it normally did from underneath the boiler. I had a good look underneath and from what I can see it is leaking from the black plastic pipe that is attached to the bottom left of the pump. However, it may be dripping further up and splashing onto it. It was dripping fairly heavily (produced about half a cupfull of water) and then stopped.

    It is now not leaking and, although the pressure when the CH was off has dropped half a bar since yesterday evening, now that the CH is on the pressure has gone up to the 1.5 bar marker.

    I cannot spot any leakage around any of the rads or any damp patches elsewhere. It's a ground floor apartment BTW.

    Am I right in thinking that to lose 1.5 bar of pressure would indicate a rather large leak? How much water would that constitute as, from what I've seen of the underside of the boiler leaking, there is not enough water coming out this way to justify that much of a pressure drop?

    I've rang up WB and they charge a £210 callout but pay for all the parts and labour. I can also sign up for their yearly coverage of £289 over installments.

    Having looked at the prices of the pressure release valves (£10 odd) and expansion cylinders (£70 odd), if it is those, then what should I do?

    Should I just get a plumber to look at it as something tells me it should be someone well versed in WB boilers and their nuances? I'm also keen to get the cover off to see if I can work out exactly where the internal leak is coming from....

    Any advice?

    Thanks

    Dan
     
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  3. Axel

    Axel

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    If you have a pressure drop while there is no drip, then the drip is not the cause of the problem, although it needs attention as there might be electrics getting wet in there.

    If it is dripping (not just while you have opened the filling loop valve) and the pressure gradually goes down while it is dripping / leaking, then that leak is at least one of the causes!

    Other possible causes of pressure loss:

    A leak somewhere in ch system (valves, pipework, possibly under floor). WB might charge you full callout but not fix problem if this was the case.

    or, perhaps when heated up the pressure is going too high (due to uncharged / faulty / insufficiently sized expansion vessel in boiler) and reaching 3 bar briefly before firing PRV and thus losing pressure

    or a dripping PRV - not closing properly. The PRV pipe should be outside, but if a loose joint then it might drip from boiler.

    One test is to pressurize boiler, leave turned off for 24 hrs with isolation valves on boiler flow and return pipes turned off (don't forget to turn back on before you use boiler again). This will establish if pressure loss is in boiler or rest of system.

    Black plastic pipe from pump might have something to do with an automatic air vent - which if faulty could leak, but you can download the manual for your boiler from WB website to establish what's what.
     
  4. AkuraEngineer

    AkuraEngineer

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    you have to understand what your dealing with here is a sealed system that’s is pressurised with water from the mains the force of the water from the mains equals the pressure in your central heating system, therefore it is possible to get rid of the pressure in the system (or charge in the system) without draining all of the water or any of the water what so ever, prime example if you live in a 3 or 4 storey house or even a 2 storey house take a pic and you bleed a radiator at the highest point of the system that's completely full of air you can take the entire central heating pressure down to zero without seeing a splash of water hit the deck

    central heating pressure loss does not technically equal water escapage loss because water is water however its just when you introduce breaks in systems integrity unless it's purpose designed (like an automatic air vent or automatic rad vents) its generally more common to find pressure loss with water escapage
     
  5. AkuraEngineer

    AkuraEngineer

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    i wouldnt do that if i was you well unless you are asuming you are going to buy new ones that is ;)
     
  6. Axel

    Axel

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    Ahh. The old 'can of worms' scenario...
     
  7. DanH

    DanH

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    Thanks guys. Yes, I hear you, it doesn't necessarily have to be a water leak that depressurises the system.

    I have not seen the pressure drop whilst it's been dripping but then again I have not been around it to see the pressure drop when it decides to do it.

    Interestingly, it's now still at 1 bar when the CH is off and when the CH is on it still at 1 bar i.e no movement when typically it goes up. So it's lost half a bar of pressure in 48 hours.

    I'm thinking that I should get a plumber out who hopefully has WB experience and not go directly with WB!

    Thanks

    Dan
     
  8. GodKnows

    GodKnows

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    Hi all,

    Make sure you get a "GasSafeRegister" gas engineer, NOT, a plumber. And when you call him, before he comes out, ask if he specialises in WB boilers. So, you don't have to pay him to say; "I don't work on this type much!" ;) After he walks up your drive and asks for a callout charge..
     
  9. DanH

    DanH

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    Thanks, will do. Regarding callouts, is it typical for a gas engineer to charge a callout to look at a problem or do some make an assessment for free?

    Thanks

    Dan
     
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  11. 123456789

    123456789

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    The expansion vessel is too small for the system and water is cooking and evaporating

    1. drain down just the boiler and re pressure vessel to 1.3bar then refill the system to 1.2

    The gauge must NOT rise

    and you may also need to fit external 12Ltr on return
    :D
     
  12. Axel

    Axel

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  13. DanH

    DanH

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    Hi guys, thanks for the answers so far and I'm going to get a gas engineer out soon.

    HOWEVER :( , as of now, when I go to repressurise the boiler it appears not to be taking in the water. The flexi hose is permanently plugged in and typically all I do is turn the tap 45 degrees downwards and it starts filling. If do that now I hear no gush of water and the pressure gauge does not move. I've unscrewed the flexi hose and checked there is pressurised water coming out so I know the supply is OK. Can the boiler simply not accept the water coming into it or is it more likely the tap is no longer opening properly?

    Thanks again

    Dan
     
  14. Axel

    Axel

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    What pressure is showing on the gauge? If the mains pressure is low for some reason it won't fill or 'gush' to any higher pressure than this!
     
  15. DanH

    DanH

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    Hi, just below 1 bar. Cold water pressure seems normal elsewhere.

    Thanks

    Dan
     
  16. DanH

    DanH

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    Eeerm, the plastic tap had broken so wasn't opening and closing the valve.. :oops:
     
  17. DanH

    DanH

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    Hi, I would like some more advice.

    A couple of days ago my girlfriend finally got a local gas engineer out who was listed on the Worcester Bosch website, but the appointment wasn't made via Worcester Bosch but rather direct with themselves.

    Although it wasn't dripping at the time, an assessment was made to fit a new AAV and pump seals (£110 in total, callout, parts and 2hrs labour).

    Unfortunately, we've come back today and noticed that the pressure has dropped significantly, about 0.5 bar and I can see it's been dripping again i.e. it's not fixed. One thing I have noticed is that there is a trace of water surrounding what looks like the boiler drain point, which is conspicuously above the DHW Cold Inlet where the drips typically end up coming from the boiler.

    We're going to call them out again but I'm wondering what the process of elinimination is for leaks/pressure drops like this? I'm assuming that my girlfriend is goin to have to pay another callout charge to chase the problem further so I want to be sure that we're experiencing the correct problem solving, if there is such a thing! Is it a case of replace a particular sequence of parts until it stops dripping!

    Thanks again,

    Dan
     
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