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Vaillant Ecotec Plus 937 - Drip from Overflow Pipe

Discussion in 'Plumbing and Central Heating' started by marktabs29, 7 Jan 2015.

  1. marktabs29

    marktabs29

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    Hi,

    First time poster after some advice regarding a Vaillant Ecotec Plus 937.

    For some time now there has been a constant drip from the overflow pipe (the pipe from where the pressure relief valve vents). The drip happens whether the boiler is operating or not. The amount of water dripping from the pipe is now truly excessive - at least half a bucket every day.

    I have recently topped up the pressure of the boiler's internal expansion vessel and also fitted a new external expansion vessel (large system - 20 radiators). The pressures are absolutely rock solid, with no wild swings in pressure, when the boiler is or isn't operating.

    When fitting the external expansion vessel, it became obvious that the drip stopped with the mains stopcock turned off, and restarted when the mains water supply was reconnected - with the boiler powered off.

    Despite the volume of water from the drip, there has never been a need to top off the system in the boiler - the cold filling pressure is constant at approx 1 bar.

    Any thoughts?

    Thanks in advance,

    Mark
     
  2. David937

    David937

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    Is it the pressure relief valve on the far left of the boiler? If it is, this is for the in-built tanks.
     
  3. marktabs29

    marktabs29

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    Hi David,

    Thanks for the reply.

    The drainage pipe in question is the one that is under the front right-hand side of the boiler and connects upwards through the bottom of the boiler to the 3-bar PRV (with a red-coloured top); looking at the front of the boiler, it is situated at the forward (near) right hand side. There are other connections cut into the pipe before it exits the house to atmosphere. I don't believe that the constant drip is through the 3-bar PRV, as the drip doesn't seem to be a function of the boiler operation, but whether the mains water is on or off. Also, there is no need to top up the CH water level/pressure, leading me to believe that the drip is not from the CH system - perhaps!

    Thanks,

    Mark
     
  4. gazdaz36

    gazdaz36

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    What is your pressure like on the cold main coming into your house.
    The pressure relief valve on the hot water side is rated at 10bar so it will take a fair amount of mains pressure to make it drip. I've only ever seen 2 go. If your mains pressure is very high then the best solution would be to fit a pressure reducing valve.
     
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  5. David937

    David937

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    When I had this problem a few months back, it was the expansion vessel at the top of the boiler under a screwed panel which needed topping up. If I remember correctly, I had to turn off the cold water and open all the hot water taps to drain the hot water before topping it up. The procedure is covered somewhere in the installers manual I believe. I haven't got access to it atm to point you to a specific page.
     
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  6. marktabs29

    marktabs29

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    Hi Gazdaz36 and David,

    Many thanks for your replies.

    Gazdaz36,

    I don't believe that the water pressure is anywhere near 10 psi, but thanks for the suggestion of fitting a pressure reducing valve.

    David,

    Having looked at the system, the 2 pipes cut into the overflow pipe were directly from the CH and DHW PRVs respectively. The drip must therefore have come from either the CH or DHW systems, rather than some other extraneous source. The pipe into the overflow pipe from the DHW system was warm, so it would appear that the drip originated there, rather than the CH system side of the boiler, as that pipe was cold.

    Checking the pressure of the DHW pressure relief valve was on my 'to do' list before I started changing the DHW PRV/the secondary heat exchanger/more expensive cures. Anyway, I also have the installation and maintenance manual, and your post prompted me to get on and check the air pressure in the DHW expansion vessel. And the pressure was - zero! Despite the number of times we've had the boiler serviced, it would be interesting to know if the pressure of the expansion vessel had ever been checked since installation. Then again, the diaphragm may have failed - I'll keep an eye on the pressure.

    The very welcome result has been that the drip - touch wood - seems to have stopped. I dread to think that the pressure has been over 10bar (145psi!) and operating the DHW PRV for such a long time. Anyway, hopefully the system will now stop losing a bucket of hot water every 2 days........

    Many thanks, David - your suggestions have been very useful.

    Regards,

    Mark
     
  7. David937

    David937

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    If the person servicing follows the manual to the letter, the CH expansion vessel would be checked annually and the DHW one every two years I think.
     
  8. marktabs29

    marktabs29

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    Hi David,

    From the maintenance section - 3 years for the check of the DHW expansion vessel pressure, to a level of 4 bar. I'm sure that we've had the boiler serviced in that time frame!

    Cheers,

    Mark
     
  9. Bunnyman

    Bunnyman

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    Mark.. David is trying to help u an u question him re the manual? Pros come on here to help not to be disrespected? Just because u had it serviced does not mean it's been done properly, many miss the Dow exp vessel
     
  10. marktabs29

    marktabs29

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    Hi Bunnyman,

    The written word................

    I am in no way 'disrespecting' David. As I have said above - I am very grateful for David's help and suggestions. His help has helped me to cure the problem with my boiler. I believe that you have thought that there was a 'tone' to my posting that certainly wasn't intended on my part. In an earlier post, David mentions that he doesn't have the servicing manual to hand; perhaps you thought I was trying to 'correct' David, whereas in fact I was trying to complete the information with respect to the required inspection interval and pressure for others who may have the same boiler as me.

    And I agree with you, despite having the boiler serviced, I suspect that the check of the DHW pressure was missed by the 'professionals'.

    Cheers,

    Mark
     
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  11. marktabs29

    marktabs29

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    Hi David,

    Just so that there is absolutely no doubt whatsoever, I would like to thank you for helping me to cure the problem with my boiler. If my post relating to the inspection time interval and required pressure came across as disrespectful, or in anyway ungrateful, I can only apologise profusely.

    Once again, many thanks,

    Mark
     
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  12. David937

    David937

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    It didn't come across as disrespectul at all, I think Bunny misinterpreted your tone :D

    I see you're based in Nottinghamshire, there is a certain engineer who occassionally posts on this forum who knows the Vaillant range very well, perhaps you should consider changing who you get to service your boiler?
     
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