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Mixer shower runs lukewarm despite actual tap being red hot to touch

Hello all,

I’m having a little trouble with the below and would appreciated some suggestions as to what the problem may be! Generally speaking I want to determine whether it’s a faulty boiler or a faulty shower, or both.

Showerforce 902-T Thermostatic mixer shower produces only lukewarm water. However, the mixer is red hot to the touch at point of connection with hot water pipe.

Water is delivered from a Worcester Greenstar 24i Junior combi boiler (situated in same room).

Furthermore, the lukewarm water sporadically turns cold for approx 10 seconds before returning to the original temperature. This coincides with the boiler cutting out, then getting momentarily louder as it fires up again.

All other hot water outlets in the flat deliver hot water as expected with not issues whatsoever. There are also no issues with the heating.

Could a faulty cartridge be the culprit? And as for the boiler, could it be a back-up of hot water in the pipes that it making it cut out?

Any advice would be much appreciated!

Many thanks,

Liam

7 Answers from MyBuilder Plumbers

Best Answer

The filters in the shower valve need cleaning out of the cartridge will need replacing. Or worst case the shower valve has been installed the wrong way round or piped up incorrectly hope this helps

2015-05-01T09:20:01+01:00

Answered 1st May 2015

Sounds like,the temperature needs adjusting on your shower if it is a thermostatic mixer then they usually come with a preset maximum temp to avoid scalding you can manually adjust this by taking the end cap or control knob off on the temperature side then turn it a little towards hot this will increase the Max temp, try it the if it still isn't hot enough repeat.
Hope this helps

2015-05-01T09:20:02+01:00

Answered 1st May 2015

I would firstly check that the hot and cold supply are fitted correctly, ( hot on the left and cold to the right) also then check that there are check valves fitted ( one way valves ) in the pipework to the mixer unit if not fitted on the inlet of he mixer, this can affect the boiler as the hot and cold can feed back up the pipes and also upset the mixer unit, if all the other taps are fine it is unlikely to be boiler related, if you eliminate those two points, check the filters are not blocked then perhaps think about looking at your thermostat cartridge.

2015-05-01T09:20:02+01:00

Answered 1st May 2015

It sounds like you've already worked it out!
Faulty cartridge and low hot water flow through boiler would be my first conclusion.
There may be some scale or grit in the mechanism for a quick repair.
If you're having trouble finding a repacement, I've found showerdoc.com have a pretty comprehensive range of cartridges.

2015-05-01T09:20:01+01:00

Answered 1st May 2015

It's definitely the thermostatic mixer.
At a certain time the thermostatic valve close completely allowing only cold water through, and stop drawing water from the boiler, that consequently stop fireing.
The faulty valve after few seconds will open (partially) again, forcing the boiler to fire up, but not enough to reduce the cold water inlet into the mixer.
I hope that help
Tiziano

2015-05-01T09:20:02+01:00

Answered 1st May 2015

Hi Liam, I would suggest this is one of two things, firstly it is likely to be the cartridge but it may be worth checking that the strainer on the hot inlet fitting on the shower bar is not clogged up with scale or other debris.

2015-05-01T09:20:01+01:00

Answered 1st May 2015

The cold taps / feed are off and still only lukewarm

2015-09-29T11:40:02+01:00

Answered 29th Sep 2015

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