Mixer Shower problems

[JamieHop]

I've just installed a Triton Cappella bar mixer shower over my bath, and ran the pipework to the shower off the existing supply to the bath taps, but the shower is freezing! When I check the flow from the bath taps, the pressure on the hot and cold are roughly equal, and the hot water runs hot! But try the shower, and it's freezing. So cold, there's condensation all over the shower pipes. I've got a gravity fed system - Cistern in the attic, and tank on the landing (same as the bathroom).

Anyone any ideas? Do I need to install a pressure reducing valve to the cold feed?

 

[ChrisR]

Is the cold on the mains or also fed from the cistern? If mains, you can try a pressure reducing valve or a pressure equalising valve, but the mismatch is too great guarantee good results.
NB pressure and flow are like volts and amps, different things

 

[JamieHop]

Cheers for the quick reply!

The cold is on the mains. Sorry if I'm being dull here, but which is best to use - pressure reducing valve or pressure equalising valve and what's the difference, if any?