Thermostatic shower runs too cold

4 Oct 2010
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United Kingdom

I've just fitted a thermostatic shower (Origin XL from Wickes, made by Bristan, I believe) which is supplied by a combi boiler in the attic (Worcester Greenstar 24i jnr).

The shower worked properly for about two days; loads of hot water and a great flow rate. However, one morning, between one shower and the next, something appeared to go wrong.

Now, with the temperature lever turned to maximum and the shower tap opened a half turn, acceptably hot water is produced but the shower's flow rate is a little low. Opening the tap further leads to a reduction in temperature until, when it is wide open, the water runs cold.

Running other taps in the bathroom while the shower is on (even those on the bath, which share pipework with the shower supply) makes little or no difference to the shower temp, although the shower's flow rate does reduce noticeably, which is what I'd expect to happen if the thermostat is working properly. It's probably worth noting that the hot taps do produce hot water when the shower is fully open (and running cold), which suggests to me that the boiler is not being asked to produce more hot water than it's capable of.

Flow rate/water pressure for both cold and hot water is excellent throughout the house - the cold being especially powerful. The combi boiler pressure is currently reading about 1.5 bar. Hot water produced by taps in the house is very hot (the boiler's manual says it's factory-set to 55degC). The hot supply pipe to the shower valve is also very hot when the shower is running and I have checked that the hot and cold supplies to the valve are the right way round. I've made sure that the maximum temperature limiter on the shower control is set as high as it can go (by removing the cap and turning the spindle all the way to the right with a pair of pliers, as outlined in the shower's instructions). The shower's spec sheet says that it is suitable for both low and high-pressure systems, the minimum requirement being 0.1 bar.

As I say, the shower did work correctly for a couple of days, which shows that the system is at least capable of supporting the shower. The valve, being what it is, is now enclosed in a false wall and is relatively inaccessible.

Now, over the last couple of days, the amount of hot water making it through the shower has gradually decreased even further. At this rate the shower will soon be unusable.

Any ideas anyone?
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have you checked the filters first ?, I haven't checked the filters yet. The shower valve is hidden within a false wall and access is....tight. I was hoping not to have to go in there and start dismantling pipework until I'd ruled out everything else.
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Fitted 2 showers of a similar design as you have bought and each time the valve had to go back to the shop. In both cases the non-return valve on the hot didn't work properly. It kept getting stuck and wasnt opening, however both the showers that I fit were not working from the start and yours has work and has now stopped. The first one I fitted, all the tiling had to come back off, and the second time I spotted it as I'd had the problem before. :confused:

If you have to remove the valve make sure you can blow down the hot and cold side of the valve and the non-return valve should open. If not then faulty valve im affraid.

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