Thermostatic shower not adjusting temperature

[dedvendies]

We had a concealed Pura mixer shower installed in our bathroom in July 2018.
IVTCV – 120mm x 280mm

This year it's slowly been getting hotter and hotter having to turn the knob more and more to mix in any cold to the point that there was barely any cold water

All the other taps in the house were fine so we contacted Pura who sent us a new TC100 - Thermostatic Cartridge.

We got a plumber who replaced it and we got cold and hot water mixing correctly again. Problem solved, but....

However, now if we have a shower and someone else in the house turns another hot tap on then the shower gets noticeably colder and vice versa, this never used to be the case as the thermostatic valve would do it's job and instantly readjust the mix of the hot and cold water so you wouldn't notice the change of the temperature in the shower. You would notice the pressure drop but never the temperature changing like it does now.

So any ideas? I guess the plumber should have checked this.
Could it be the thermostatic cartridge replacement is broken? Or a different problem?

I have a Valiant ecoTECexclusive835 boiler if that matters, but as said, everything was working great into recently.

Thanks.

 

[oldbuffer]

1. Sounds as if the boiler can't supply enough hot water. Consider having the hot water heat exchanger checked, particularly if you are in a hard water area.
2. If you engaged the plumber to change the thermostatic cartridge, he / she would have no reason to check other parts of your system.
3. If you engaged the plumber to check your system over completely, then he / she should have detected the issue.

 

[dedvendies]

Hi there, thanks for the help, appreciate it.

I did a few tests.
I turned the kitchen tap, upstairs bathroom tap and shower all on at the same time at their hottest setting and they all stayed incredibly hot at the same time.

I guess this suggests that the boiler isn't having issues with heating enough water all at once?


As another test I set the shower to a medium setting so it was warm.
If I then turn the tap on in the bathroom at the same time at its coldest setting the shower gets really hot.
Doesn't this suggest that the thermostatic cartridge is at fault as it should regulate the hot water to make it less hot?