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Plumbing again - pinhole leak in hot water cylinder

Discussion in 'off topic' started by RichardH, May 16, 2010.

  1. RichardH

    RichardH Bodging pleb

    Just spotted a steady drip from under the HWC, and once I managed to get at it (it's stupidly built into the corner of a kitchen, with the only access via lifting the worksurface (which also holds the sink, just to make it even more irritating).

    The insulation was sodden, and once I'd managed to strip it back I found that the leak was a pinhole in the "shoulder" of the cylinder where the immersion heater screws in.

    I'd have thought that area was stronger than the rest??!!

    Anyway, I part drained the cylinder, cleaned down and got some Plastic Padding Leak Fix made up and applied liberally.

    It seems to have solved the problem, but should I be worried about more leaks like this appearing? Not sure if it's relevant, but we're in a hard water area, and the tank's probably around 8 years old.
  2. Radfordman

    Radfordman pfm Member

    I had almost exactly the same, but tank is much older. I tried soldering the tiny hole, but could not get enough heat into the tank. Cleaned it all up and just used Araldite (original slow cure). That was about three years ago and it's still fine.
  3. Wilky

    Wilky pfm Member

    Hi Richard.

    Usually the immersion boss would a thicker gauge copper than the side walls, but it's possible that it was malformed/weak from the day it was manufactured.
    It might also have been damaged by the force applied when the immersion heater element was installed.

    If your repair doesn't hold, drain the cylinder completely, cut open a small piece of 15 or 22 mm copper tube and flatten it out to create a small sheet.
    Trim and 'dress' the patch to cover the area affected, then clean and tin the affected area and the patch.
    Sit the patch onto the cylinder, heat sufficiently to get the solder to flow and feed in a little more between both.
    Let it cool and wipe of any flux residue.

  4. Colin Barron

    Colin Barron pfm Member

    Think laterally if the repair does not work fit a bosch condensing combi boiler, the old boilers may have less to go wrong with them but unless you are on a scheme where you do not pay for usage then they are a very expensive option.
  5. Mullardman

    Mullardman Moderately extreme...

    Sound advice Dave, but there seems to be a bit of a blow torch phobia operating here. They all want instant fixes. So reflective of the current state of society.! :D
  6. Wilky

    Wilky pfm Member

    Oh I don't know if that's the case with Richard.
    Looking at some of the projects he's tackled in the past, I'm sure it's well within his scope.

  7. Radfordman

    Radfordman pfm Member

    In my case I tried soldering with a 100W soldering gun. It did not seem to provide enough heat. Unfortunately, I had my garage broken in to just before the tank leak and my large collection of tools was stolen (including gas blow torches etc.) The theif knew what they were taking as my CO meter was in one place and the probe was on a hook on the wall, both went.

    Years later, I still have not gone through the garage properly to list my losses. I find it difficult. There was a tremendous tool collection. I first realized that the garage had been raided when I looked for a tracking tool to lend a friend. It was not there, nor many other items.
  8. RichardH

    RichardH Bodging pleb

    Cheers folks - in the main I wanted condirmation that this was likely to be an isolated weakness, and not indicative that the whole tank was about to start springing leaks.

    I'll keep an eye on my repair, and if it proves ineffective, then it may actually be a tank replacement job, as I think it would be very hard to dress some copper to fit into the complicated curves that the pinhole is located - also it's all now gunked over with my epoxy stuff ;)

    (And Dave - thanks for the vote of competence - someone once asked me if my hobby was plumbing (I had just completed a load of work on the main bathroom) - I'd have to say my hobby is now more swearing when I have to do some plumbing ;) )
  9. RichardH

    RichardH Bodging pleb

    Well, it's sprung a leak again - around the same place. I've mixed up some more epoxy and smudged that in, and am keeping my fingers crossed.

    However, I think it may be time for a new tank.

    Is it worth considering stainless rather than copper? We're in a hard water area, and given that it's heated by an immersion, I worry about scale build up inside. If we do go for a new tank, I'm tempted to change the location so it's no longer buried under a work surface - then we can get a larger (standard size) tank too.
  10. zener

    zener fluff

    Richard , can you pop the element out and patch from the inside with the epoxy stuff aswell.
  11. Mullardman

    Mullardman Moderately extreme...


    Sorry to hear you were robbed. Not good.

    If it was me, I'd spend some time cleaning off the epoxy. (Maybe use a powered wire brush? Obviously with care, not to rip away the copper.

    I'd also invest a fiver or so in a cheap-ish blowtorch from B&Q. They can be a bit unpredictable, but I plumbed in a new bathroom, shower etc., with one (and with a lot of remote guidance from Dave (Wilky) but they do the job.

    Might be easier to make a patch if you anneal the copper regularly (Heat to red heat, quench in water) then clean up well before soldering.

    However. If the hole really is only a pinhole, have you considered just sealing it with a good blob of solder? Plumber's solder can be 'wiped' if necessary. I'm sure Dave knows more about how to do that.

  12. RichardH

    RichardH Bodging pleb

    Robbed? Not me.... thankfully.

    I have a decent blowtorch already thanks. I used it to completely plumb my previous house's bathroom, as well as a fair bit of this house. So I am not averse to some DIY.

    It's all well and good to have this talk of fixing the leak with solder, patches etc. However, the position of the tank makes it almost impossible to access. As far as I can tell, it's on the "neck" of the threaded insert for the immersion heater. So it is hard to patch either from inside or outside. The leak is also facing away from me, and the only way to access the top of the tank is to hinge the kitchen worksurface up and prop it - so you're working in semi dark through a letterbox and without clear sight of the affected area. Try soldering that.

    To get better access would mean a whole lot more pain and upheaval. This is why I'm thinking I'd be better off biting the bullet and moving the tank to a more sensible place.
  13. Radfordman

    Radfordman pfm Member

    Are you using the original slow set epoxy? Much better in my view that the fast set ones.
  14. Mullardman

    Mullardman Moderately extreme...

    Apologies. It was Radfordman wot got robbed.

    Well, if it is that difficult to access, I guess it's going to have to come out. You then choose whether it's worth repairing and re-fitting, or replacing and moving.

    I had a copper tank for many years. It had a heat exchanger for the central heating, which leaked at the unions with the tank wall a number of times.
    It also had an immersion heater. Several elements failed over the years and had to be replaced. The final one caused an explosion in the immersion heater cap and the consequent emptying of the header tank into the dining room, via, the ceiling., which also had to be replaced, along with the tank.

    I went for a Combi, which has already paid for itself in better efficiency and (so far) no problems. If I had to completely replace it tomorrow, it would still be less of a pain than the old system.

  15. RichardH

    RichardH Bodging pleb

    Well, I've tried using some of that epoxy putty on it for the moment - fast setting, but has the benefit of holding its form rather than slumping down.

    Mull - you're right, it will have to come out at some point. Probably half full of scale, too.

    It's actually a secondary tank that serves a part of the house that you could call an annex. Having said that, you could be right re the combi thing - if we have to pay someone to come in and refit a tank and disrupt everything, then the money might be better put towards a combi. There's a thought...
  16. Fox

    Fox The sound of one hoof clopping

    No... choose coppper if replacing. far far safer.
  17. RichardH

    RichardH Bodging pleb

    Interesting - why do you say that? Is SS prone to rupture then? This is a vented cylinder, so there's no mains pressure.
  18. Fox

    Fox The sound of one hoof clopping

    Copper better for dealing with Legionella and e-coli, its lethal to it and harmless to humans as water storage. Lots of data out there to back this up. Google. For me this is an issue as I have a rural water supply. I filter it all and sterilize it but it still is possible for contaminants to thrive in it.

    ...additionally copper is a more efficient conductors of heat. It has a thermal conductivity of 401W/mK (Stainless Steel is rated at ~14-18W/mK -- depending on purity) The new 250L vented copper Gledhill Horizontal cylinder we have just had fitted is vastly superior to the old 90L vertical one the house came with and was fitted in the 1960s, no leaks in ours BTW we just wanted more hot water storage. Additionally in a modern cylinder the base is thicker and the nut mount for the immersion heater has a thicker mounting boss (not the case on older ones, yes it can be very thin and you can damage it easily if you ever needed to change the immersion heater as they stick over time). Ours is a custom unit made with horizontal solar battery, secondary hot water heating system fittings, secondary water fittings plus a dedicated pumped fitting for the pump-assisted shower (negating the need for a surrey flange) -- all in all a fine solution.

    Also I don't trust the purity of much of the steel/chromium mix in stainless these days. You can get very pure stainless (what you need for a storage tank) but by then its very close to copper prices and we get back to the legionella/e-coli issue which Stainless is no good at.

    Utterly personal reasons -- but there you go. There is a good readon why copper is used but Stainless has become an option mainly because of copper's scarcity and price.
  19. fullahead

    fullahead pfm Member

    If the metal in that area is reasonably thick ,you could try "pinging" it.Try to locate the pinhole and give it a tap with a centre punch,it spreads the metal and sometime covers over the pinhole.Often worked for me in engine cooling pipes when I was at sea. Problem with sticky stuff type methods, is that it has to be absolutely dry to be effective.
    good luck
  20. colasblue

    colasblue pfm Member

    If you can possibly avoid it don't attempt to remove the immersion heater!

    They are difficult to remove and you have a significant chance of wrecking the cylinder if you even try. The pro's don't even want to try it if they can avoid it.

    If you must then you need to get a special spanner (get it from a proper tool shop - not a cheap crappy B&Q thing) and you need to get the spanner on the heater and give it a good hard sharp wallop in the right direction with a large club hammer. It will either come out or it won't and if it won't your cylinder's done.

    What Wilky suggested is the best way to do it. The epoxy stuff will give out after a while due to to the continual expansion and contraction of the cylinder.

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