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Discuss Power shower too hot! in the Bathrooms, Showers and Wetrooms area at

  1. Peter Laing

    Peter Laing New Member

    Hi All,

    First post here, so hoping someone can help me. I'm not a plumber, but an avid DIYer and keen to work out things for myself.

    Our house has two power showers fed from the same pump in the airing cupboard. We have a hot water tank in there and two cold water header tanks in the loft - the second one apparently just feeding the pump for the showers.

    The problem is that whereas both showers would need the mixer/on-off tap set to at least half way to get the shower to a suitable temperature (it's been that way since we moved in 2 years ago), very recently it's suddenly changed so both the showers are ridiculously hot unless you only turn the tap on less than a quarter, i.e. where it would have been only luke warm before.

    I've checked the temperature of the hot water feed and it's around 60 degrees, which is what the thermostat on the hot water tank is set to, so it's not the hot water being too hot - it's the cold water not having enough pressure I assume.

    I've been up in the loft and worked out that the cold feed for the pump comes from a secondary header tank, which is fed from the bottom through a short pipe from the main header tank next to it. I cant see any restrictions to flow, though both tanks have loads of white stuff at the bottom - more so the secondary tank, which just has one feed in from the main tank and one feed out to the pump.

    So, any ideas why the showers are running too hot? Pump isn't making any unusual noises.

    I've got another issue, which I don't believe is connected (although it happened about the same time) with the central heating pump being on 24/7 even when the heating is off - I'll post that separately.
  2. Best

    Best Trusted Plumber Top Contributor!!

    What sort of shower valves have you got?
    The cold side could be blocked and each shower might have inbuilt filters, but strange that both showers would have cold side filters blocked suddenly at same time. Perhaps more likely the pump is where the problem is. It also can have filters on the inlets.
    Or you have a pumping problem with the cold side of pump and it is only partly pumping cold water.
  3. SimonG

    SimonG Trusted Plumber Top Contributor!!

    Filters or cartridge
  4. Peter Laing

    Peter Laing New Member

    Hi Simon, thanks for the prompt response. Unfortunately, I'm no expert in these matters, so I'm not sure what you mean by filters and cartridges - where are these fitted normally?
  5. Peter Laing

    Peter Laing New Member

    Sorry Best - just realised you had replied too. If, by shower valves, you mean the control in the shower cubicle, they've just got GROHE written on them. It's just a single control that you rotate anticlockwise to turn the water on (that kicks in the pump), then the further round you turn it, the hotter it gets.

    From what I can make out of all the pipes in the loft, the feed from the pump goes into the loft, then splits two ways - one for each shower.

    It does puzzle me that both showers developed the same problem at the same time. Whilst running the shower as cold as possible (i.e. minimum turn just to get the pump kicked in), I placed a finger near the outlet from the secondary header tank that feeds the pump and was surprised how strong the pull was - got worried I'd get my finger stuck in the hole!

    I haven't checked if there's any blockage on the filters on the pump inlets - perhaps that's where I should go next.
  6. jtsplumbing

    jtsplumbing Plumber GSR

    Think you have ordinary shower mixers and not Thermostatic ones ! if that's the case for safety I would replace with thermostatic mixer valves.
  7. Best

    Best Trusted Plumber Top Contributor!!

    I think they could still be thermostatic shower valves, but are the single control type with as you turn it - full flow, then cold, then warmer.
    I don't like that type because it is always full flow, but they less expensive than the dual control valves
  8. Best

    Best Trusted Plumber Top Contributor!!

  9. Peter Laing

    Peter Laing New Member

    Thanks for your responses, but no matter what type of valves I have, I cant see that they're the source of my problem as it's unlikely both would have failed at the same time. I'm not beginning to think this problem is linked to another issue I have with the central heating/hot water pump and boiler running all night, despite the timer/controller saying it's off. I've put a separate post on this on the central heating forum - see here:

    Hot water staying on all night despite controller being off
  10. Best

    Best Trusted Plumber Top Contributor!!

    Motorised valves are a very common fault for keeping power on constantly to boilers and heating circulating pump, so get them checked.
    The 2 port motorised valves have a micro switch that has a permanent live wire and if switch remains on, power is constant to boiler and pump
  11. Peter Laing

    Peter Laing New Member

    Thank you Best - makes sense now. I'll check them out.
    • Like Like x 1
  12. jtsplumbing

    jtsplumbing Plumber GSR

    More than one item failing at the same time is not uncommon , but Your problem is with temperature which without knowing the model of your mixers would point to them being the non thermostic type, so the higher temperature of your stored water will affect the showers temperature, less likely to happen with thermostatic mixers .
  13. Peter Laing

    Peter Laing New Member

    Hello again and thanks for all your suggestions and advice. I think the problem is now cured. Basically, I took the "box" off the front of both two port valves and tried to move the spindles on the valve with pliers - the heating one moved very freely, but the hot water one was much harder to move. I exercised it back and forth a few times and it did free up, so I put the the box back on it and it appears to work now!

    I've monitored it for a couple of days now and I've seen the black lever on both valves move from open to closed when they should do, i.e. when the controller says, or the thermostat kicks in/out.

    Double bonus is that our showers are both now operating at normal temperature too! Happy bunny. I'm not counting too many chickens though as chances are, it'll stick again, in which case I'll get it replaced.

    Thanks again for all your help!
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