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Discuss Gledhill light unvented cylinder imploded in the Plumbing Forum area at

  1. Rakesh

    Rakesh New Member

    Hi everyone,

    Hope someone can shed light on this problem.
    I’ve been and changed bath taps For a client by first isolating the cold mains.
    I then opened the kitchen mixer tap to drain both hot and cold water and while that was draining, I went into the bathroom and opened the separate hot and cold bath taps.
    The water started to slow down but the hot took a little longer to stop (no more then 1-2mins).
    So I proceeded to remove the bath taps then suddenly the hot water started running from the pipe. At this stage the tap was already removed so I had to place my finger over the pipe to stop the water.
    I asked the client to open the taps downstairs to which he replied “they are already open”
    He then went into the loft to isolate the hot water outlet from the cylinder via a gate valve he had installed by the installer of the cylinder.
    After replacing the taps, I asked the water to be switched back on and all looked well till the clients son shouts out that the boiler is leaking.
    I went up into the loft and saw that the cylinder was leaking from the heating outlet into a polythene sheet made up into a box.
    I isolated the cold mains and although the cylinder looked fine externally, the top had come away and the secondary outlet that was unused had moved away from its original position and poking out into the insulation of the cylinder away from where it should be. It was obvious that the cylinder had imploded and went near back into shape once the water was put back on.
    At this point the client says to me “not again”
    He then explained that that’s the second cylinder that’s imploded the first one five years ago and now this one. Apparently the first one imploded after the client changed a washer in one of the taps.
    The cylinder is installed in the loft and it’s a detached 4 bedroom property with 2 bathrooms.

    On inspection, the only thing I noticed is that the expansion vessel is installed on the hot water outlet instead of being installed after the combination valve on the cold inlet as illustrated on the manual
    Would this void the warranty and cause such problem?








  2. bogrodder

    bogrodder Plumber GSR Top Contributor!!

    The cold water supply to cylinder from the multifunction valve is coming off the wrong port.
    • Like Like x 1
  3. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    First things first are you G3 qualified?
    • Like Like x 1
  4. bogrodder

    bogrodder Plumber GSR Top Contributor!!

    Ah... yes ! Good call, I’m still wiping sleep from my eyes.
    • Like Like x 1
  5. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    No worries mate. As you said though I’d say piping issue
    • Like Like x 2
  6. Rakesh

    Rakesh New Member

    Neither am I gas safe no am I G3 qualified
    I’m a competent plumber and install bathrooms for a living.
    I’m not installing or touching the cylinder. I’m trying to get myself out of the liability and also to help my client resolve this issue.
  7. Rakesh

    Rakesh New Member

    I had also noticed that.
    Looking at the manual, it’s not in the right orientation.
    The main thing I noticed was the expansion vessel.
    They may be other problems but as I’m not G3 qualified, I can’t comment on the installation.
    I just want to arm myself with as much information for the client to either get a replacement cylinder or get the installer to take liability.
  8. Riley

    Riley S. Mod Trusted Plumber GSR Top Contributor!!

    Then first things first get a G3 qualified engineer in to assess the situation. My guess is that no one checked the install was correct on first or second install so I’d say you’re ok
    • Like Like x 1
  9. oz-plumber

    oz-plumber Plumber

    I hope you have insurance!!!!
    • Dislike Dislike x 1
  10. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    Your client needs to go back to the guy that fitted it .
    • Like Like x 2
  11. Rakesh

    Rakesh New Member

    I’ve just been searching for G3 qualification.
    First thing that came up on the search was Gledhill g3 corse. 1 day £90 to become G3 qualified??
    I would do the course just to have that qualification.
  12. Tim S

    Tim S Member

    The installation has been incorrectly installed and should not be used
  13. SimonG

    SimonG Trusted Plumber

    Incorrect installation, tell customer to contact the manufacturer for their take on it.
    • Agree Agree x 3
  14. Brambles

    Brambles Member

    If you can persuade the Client, I would get Gledhill out to view and comment on the installation / collapsed tank.

    Whilst you don’t need to be G3 qualified to change washers et al on a pressurised system, you really do need to understand the principles of how the system operates and the importance of venting when draining it down.

    Often these things are not clear cut.

    Personally, I don’t think that the G3 course covers sufficient detail about the process and need to avoid the creation if a vacuum in an unvented cylinder. It is very easy to do this unintentionally when draining down an unvented system when the tank is at or near the highest point of the installation. Draining off bellow the tank with the cold water supply isolated has the potential to create a vaccum in the vessel. I suspect this is part of the problem here - or did you ensure that the tank could freely vent either from the prv or preferably by slackening the hot water draw off connection.

    Think of the tank like a crisp packet - it takes a hard blow to burst it, but only a very gentle suck to collapse it.
    • Agree Agree x 5
    • Like Like x 2
  15. YorkshireDave

    YorkshireDave Plumber

    100% agree. However! This needs to be done by the customer. The reason for that is if you do it then you become kind of 'tainted' by association and the customer needs to understand you are stood alongside them rather than doing it for them - hope that makes sense?

    Def def def get them in. Once that's done then the customer can call the last installer back to correct it. Even if the last installer simply replicated what was there, they still have a duty of care to do the job properly. Obviously, if they were not G3 then that's yet another issue.

    My advice? Stay 'close', help, but not too much.

    Let us know how you get on.

    PS. The course is well worth doing, BUT prepare to spend the rest of your life learning what's NOT taught ;)
    • Like Like x 2
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