Faulty Thermostatic mixer valve

[sailorf80]

I have a Thermostatic mixer fitted in my shower downstairs which has always worked well since fitting about 2 years ago; however over time the need to adjust towards the hot water side has increased gradually meaning that now in order to have a warm shower the mixer has to be turned up to the maximum.
The problem is that it cannot be adjusted any further and the shower is getting cooler and cooler as the weeks go by.
Is this a common fault and is there anything I can do? To replace the valve will be very difficult (it's embedded into the wall with the pipework behind the tiles). We do live in a hard water area and assume that a possible restriction of flow may have occurred, but just wanted to know if any members had come across this and maybe had a solution.
Here's hoping.

 

[ChrisR]

First crank the tem pfrom max to min amnd back several times. SOmetimes that'll shed enough limescale to get it back working again.
Otherwise, try to identify it. Usually you can change the cartridge from the front. If it's anonymous, sometimes descaling and greasing it, once it's out, will work.

 

[sailorf80]

Chris, sorry not to reply, I've had PC snags as well as plumbing ones! I have tried the back and forth routine without success and have now taken the cartridge out.
It is as you suggested anonymous so I have it now sitting in descaler and will try it again after a good soak. Thanks very much for the advice.

 

[sailorf80]

Did all as suggested and put it back in, unfortunately the problem is still there so I'll have to try and source a new cartridge, a bit of a nightmare as the damned thing has no makers markings on it. Oh well, nothing ventured nothing gained, thanks again for the help.

 

[Gasguru]

Sometimes they just need "re-calibrating" ie rotate the temp control to maximum, pull off the temp control knob/ring and then rotate the valve temperature spindle in the hot direction a little more, then replace the control knob.