Bathroom hot water hot/cold

[Chester]

I have a job on a house where the shower cartridge is faulty (seized solid) however the basins and bath/shower filler in all 3 bathrooms are putting out hot water which goes cold then warm back to cold, the kitchen tap downstairs runs nice and hot and they have an outhouse close to the kitchen which has a sink in it which runs hot aswell, in said outhouse is a large biomass boiler, I'm not very clued up on these, theres an awful lot going on. I'm convinced there is a TMV tucked away somewhere in the house that's feeding the bathrooms. Currently to run a hot bath they are running the cold on the basin at the same time as filling up which is helping. Any thoughts would help out, the house is quite old (farm) and very large, it had an over haul at some point in the past on the bathrooms. Cheers.

 

[JCplumb]

Possibly cold overpowering hot in the broken shower valve, if replacing the shower cartridge doesn't sort it bung an NRV on the hot feed to the shower.

 

[king of pipes]

Isolate the hot and cold supplies to the faulty shower to see if this sorts the problem out then plan the shower repair or replacement. Kop

 

[Burger]

Unusual to have a TMV feeding all bathrooms, are any of the taps new? Could be those that are allowing the cold main to overpower the hot, or they could have TMVs fitted. You need to ask how long the issue has been going on for.