Bristan Mixer Shower Keeps Going Cold

[Bazza4465]

I have a Bristan mixer shower that keeps going cold, it goes cold for a minute or so and then comes back hot before going cold again. I have replaced the cartridge in the shower and also replaced the shower hose, there was a slight improvement for a week or so but it is now back to what it was like before. I have the same model shower over the bath and there are no problems with that so I assume the problem is with the shower itself. Any advice to help sort this out would be appreciated.
Thanks
Bazza4465

 

[ShaunCorbs]

Hot and cold pipes in the right way ?

Always done it or just started ?

 

[king of pipes]

Also what boiler do you have is it a combi by any chance ? Cheers kop

 

[Bazza4465]

Hot and cold pipes in the right way ?

Always done it or just started ?

 

[Bazza4465]

This has only started over the last few months and slowly got worse. The shower is a number of years old and worked okay before, nothing done to the pipework so the hot and cold are in the right way round.

 

[Bazza4465]

Also what boiler do you have is it a combi by any chance ? Cheers kop

 

[Bazza4465]

The boiler is a combi, it is a Worcester CDI.

 

[ShaunCorbs]

All other taps ok ?

 

[steadyon]

If its has them, check the non-return valves and filters in both inlets.

 

[Bazza4465]

I have the same shower over the bath in the same room and there are no problems with that.
How do I get to the non-return valves and filters to check them, do I have to take the cartridge out?

Thanks for your responses.