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Cold water from hot taps although cylinder hot!

Hi, I really hope someone can help on this one!
I've had no hot water since last Wednesday, even though the heating is working and the hot water cylinder and all the pipes in and out are really hot. Everything was fine until I had a new hand basin installed in my bathroom on Weds. The plumber turned the water off in the airing cupboard and when he left I realised the water coming out of the hot taps was cold. To cut a long and frustrating story short, four days later and after four separate visits from two plumbers and two heating engineers I still have the same problem. We've gone through various solutions - airlock (plumber said there isn't one) and testing all the taps and valves on the pipes - and everyone is stumped. The cylinder is hot, the pipes are untouchabley hot and the water flow from the taps isn't spluttering or inconsistent. I turned the hot water of about 8pm last night as it seemed pointless to keep heating it up but even now the pipes in and out of the tank are still really hot. The only other out of the ordinary thing that happened on Weds was I had a new fuse box fitted so the mains power was out for a couple of hours.
One of the plumbers mumbled something about the shower mixer valve maybe drawing cold into the hot water supply...but he didn't think this was worth looking at so I don't know how likely this is!

If anyone can help or throw some new suggestions at me i would be extremely grateful.

Thanks so much for taking the time to read this. :)


  • Paul48Paul48 Posts: 4,492Member
    edited November 2015
    Have you closed the stop valves to that new basin? The same problem can be created when leaving a test plug in a new shower valve. Just putting that out there...not knowing specifics of what has been done.
  • JStarJStar Posts: 2,668Member
    There must be a cold and hot line bypassing somewhere. Do you have the ability to isolate each fixture?
  • MeliMeli Posts: 15Member
    Thank you, Paul48 and JStar. As far as I know all of the valves and taps have been opened and closed several times. It does seem to me that the water from all the hot taps is being drawn from some place other than the cylinder - otherwise why wouldn't it be hot? - but I don't know how it can be. I live in a flat roofed house so have no loft and the feeder(?) tank is in the airing cupboard just above the hot water tank. I'm just being passed around from plumber to heating engineer as no one knows what to do!
  • MeliMeli Posts: 15Member
    Hatterasguy - no, the water from all the hot taps is as cold as the mains, even if I leave it running for ten minutes or more. Thank you for commenting :)
  • JStarJStar Posts: 2,668Member
    Do this quick test:

    Turn off the water valve that supplies the water heater. Then open the hot side of the faucets. If water comes out with pressure, you are bypassing cold water somewhere.
  • MeliMeli Posts: 15Member
    Hatterasguy - so sorry!! Obviously didn't read your question properly. No, the cold taps have cold water too.
  • MeliMeli Posts: 15Member
    JStar - I'm not sure which pipe supplies the cylinder. There's a pipe going into the bottom, with three round red taps on which are all open, and one slightly higher up that has an actuator switch and splits into three. The very top pipe is the one that supplies the taps, I think.....I'm hoping I've attached a photo to show you.
    Sorry, I'm a bit useless !
  • MeliMeli Posts: 15Member
    I'm hoping that the photo I've posted will work....
  • MeliMeli Posts: 15Member
    Take it you haven't yet?
    Just tried adding the photo again.
    I really appreciate you taking time to try and helpme.

  • MeliMeli Posts: 15Member
    It is when I open it! What are you seeing??
  • MeliMeli Posts: 15Member
    It shows me the whole of the water cylinder up to the boiler - and the only valves I can see are the tree red round taps.
  • MeliMeli Posts: 15Member
    The photo shows the airing cupboard - the hot water cylinder takes up most of it and the boiler sits above it. I opened the airing cupboard door and took the photo. I think the plumber must've turned off one of the three red taps.
  • MeliMeli Posts: 15Member
    Ok, just turned the left valve off, ran the hot tap but it made no difference.
  • MeliMeli Posts: 15Member
    The pipe is very hot! It goes to an upright pipe which the plumber said supplies the hot taps upstairs and down. You can just see this on the left side of the photo - it's got a T bar connector. The upright pipe stays cold when the taps are running but the straight pipe from the top of the cylinder stays hot.
  • JUGHNEJUGHNE Posts: 5,727Member
    You mentioned earlier some plumber (just curious would you call him a "fitter" or not?) I've been a couple places in my life and wonder where in the Commonwealth you might be located if you don't mind my asking? Or I beg your pardon if I am way off base?

    But the plumber talked of the shower could have back flow devices or thermostatic blocks that have shut down the hot for whatever reason and is sending cold everywhere else. That is a long shot. The second guess is someone at the cylinder/tank reversed a check valve on the hot tap from the tank.
  • unclejohnunclejohn Posts: 1,374Member
    I see a three way valve in that picture. There in most likely lies your trouble.
  • MeliMeli Posts: 15Member
    Hatterasguy - I've followed the pipe as far as I can (the pipe goes down into the floorboards and up into the ceiling) and there are no valves or taps along it's length.
  • MeliMeli Posts: 15Member
    Jughne - Hi! I'm in England and we tend to call anyone fiddling with our pipes a plumber. If the shower thermostatic valve is playing up would it affect every hot tap, even if the shower isn't on?
    I just keep thinking it must be something so simple......
    Thank you for your help.
  • MeliMeli Posts: 15Member
    Hi Unclejohn! I've opened all of the red valves fully but it's made no difference. Should they all be open?
    The other thing is it took 36 hours for the pipes to and from the cylinder to cool down after switching the heating coil off. It's never taken this long before so would that have anything to do with it?
    Thank you for helping :)
  • 4Johnpipe4Johnpipe Posts: 479Member
    Can you get us a picture of your boiler above the cylinder? Also there should be a cold water pipe feeding the cylinder can you see that?
    Considerate People, Considerate Service, Consider It Done!
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  • HillyHilly Posts: 403Member
    Any progress of this @Meli
  • ArchieGodfreyArchieGodfrey Posts: 1Member
    Did you discover the reason for this. A customer of mine has the same problem. Was if the shower mixer valve?
  • ZmanZman Posts: 4,975Member

    Did you discover the reason for this. A customer of mine has the same problem. Was if the shower mixer valve?

    Start a new post and give the details of your problem.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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