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Leaking shower mixer?

Discussion in 'Plumbing and Central Heating' started by daveaspy, 28 Jul 2019.

  1. daveaspy

    daveaspy

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    All has been fine with the shower and bath until the last few weeks where the bath mixer tap wont supply very hot water and the shower is often luke warm too, even when on max temp (reducing flow doesn't seem to help). All other taps seem to be fine - too hot to hold your hand under.

    A bit of reading suggests the shower mixer maybe at fault, with talk of adding non return valves an option. I turned off the combi boiler and isolated it's cold water feed but was still getting a strong flow out of all the hot taps which supports the mixer fault I think. I cant think where else there could be a crossover of cold water into hot pipes?

    Now, I have a concealed Grohe mixer but I'm not 100% on the model (it was in the house when we moved in 7 years ago, could be much older) - can anybody identify it?

    shower.png
    shower1.png
    I'm thinking maybe a Grohe Grohetherm 3000 but there are others that look similar inside - I cant find anything with that front plate though! It would seem to have inbuilt NRVs - is it worth me replacing these? They look to be about 20 quid each (for the 3000) but I don't want to waste my cash if it isn't the right fix. Would it tell me anything if I swapped the hot and cold NRVs over? I cant see any isolating valves other than the main stopcock unfortunately.

    Any thoughts?
     
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  3. ktuludays

    ktuludays

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    Just swap the heat control valve. My grohe concealed mixer failed 2 years ago with the same issue swapped the valve and been fine ever since.
     
  4. daveaspy

    daveaspy

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    I took out the NRVs and gave them a rinse/wiggle and that seems to have resolved the bath problem - it is now mad hot and I'm getting nothing through the hot taps when cold feed to the boiler is isolated.

    However the shower still doesnt get past luke warm so will look at the thermostatic capsule - but yikes they are expensive! Its a 47450 which is generally around £120 although I've just found superbath are doing it for 63 which isnt too bad. Going to give it a clean with vinegar and see if that sorts it first. It looks like cold water goes in the bottom and comes out of the gap - on hot that gap does close tightly but there is also a little bit of scale around the edges which might cause it to pass a bit? May also be some passing at the rubber seal between those two arrows?

    therm.png
     
  5. ktuludays

    ktuludays

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    I think mine was circa £70 from amazon uk
     
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  6. daveaspy

    daveaspy

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    well a good clean of the gap surfaces in the mixer control seems to have sorted the problem, for now at least. I've got a really good range from freezing cold to scalding hot :D

    I still think there might be a slight leak on the NRVs as when the bath tap is running just on hot and the shower is off - twisting the shower heat control does make the flow sound different although the tap still runs hot so I think I'll just leave it for now until things go bad again :D
     
  7. ktuludays

    ktuludays

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    Thanks for reporting back
     
  8. DIYnot Local

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