Shower mixer affecting bath hot water temperature

[Daddy Boots]

Bathroom was new installation 18 months ago with a separate Crosswater shower unit with thermostatic mixer and a separate bath running off a combi boiler. The shower was taking longer to heat up. Had the boiler checked out and the engineer said it will take longer as it's cold in winter. However also noticed the temperature of the bath hot water if affected by the position of the shower valve. When the shower valve is set to cool ( and not even running) the bath hot temperature is significantly less than when the shower valve is set to max. Boiler engineer suggested their might be something to do with the the pipework to shower/bath. Can't access any pipework as it's now all tiled. Any ideas on a fix ?

 

[Stuckinarut]

How old is the property?

 

[Wayners]

Cold water pushing back through and mixing with hot water which Is coming out cooler than it should?
We have mixer taps at work doing that.

 

[Daddy Boots]

Property is 1920's. The shower and mixer is totally separate from the bath. It was only by chance we found playing with the shower mixer thermostat with no flow through the shower affected the hot water temperature when running the bath.

 

[Stuckinarut]

Property is 1920's. The shower and mixer is totally separate from the bath. It was only by chance we found playing with the shower mixer thermostat with no flow through the shower affected the hot water temperature when running the bath.

So that should rule out a TMV under the bath, could be as above then passing mixer, could also be a boiler problem. Do other outlets get hot? Which make and model of boiler?

 

[Daddy Boots]

Worcester Bosch Greenstar junior 28i All other outlets ok. The hot in the washbasin gets very hot once it gets going compared to the bath no doubt due to the flow rate. Nevertheless, the temp of the hot on the bath is affected by the position of the thermostatic valve on the separate shower when it's not even running. If we have a normal shower and forget to turn it up to max when we've finished then the next bath doesn't run hot enough.

 

[Stuckinarut]

Worcester Bosch Greenstar junior 28i All other outlets ok. The hot in the washbasin gets very hot once it gets going compared to the bath no doubt due to the flow rate. Nevertheless, the temp of the hot on the bath is affected by the position of the thermostatic valve on the separate shower when it's not even running. If we have a normal shower and forget to turn it up to max when we've finished then the next bath doesn't run hot enough.

I would say it all points to that shower. Do you know if there’s isolation valves fitted?