Hoping someone can solve this very annoying issue.
I have a Gainsborough GS500 thermostatic mixer shower fitted above the bath in my flat. I have an Ariston microGenus II 24kw combi boiler in the kitchen.
I had been having problems with lukewarm water from the shower - the kitchen hot tap runs boiling, the bathroom sink hot tap runs boiling and the bath hot tap runs boiling when not turned on full - fully open it only runs lukewarm. I was told that I needed to replace the thermostatic cartridge in my mixer shower. I bought this (expensive) part and paid for a plumber to come and fit it but it hasn't solved the problem! The plumber didn't seem to have any other ideas and said it had to be the boiler. I rang the company that fitted my boiler and they said it wasn't the boiler and suggested the cartridge needed calibrating or it was faulty. All I am getting is lots of conflicting advice and astronomical quotes to come and have a look - but no one seems certain of what the problem/solution is.
Please can anyone give me some clear advice and estimations of how long/how much it would be to fix the problem