Shower install - gravity fed query

[LeeUK]

Ow do

I'm installing a shower in an ensuite and as we have a good bath pressure I'm giving it a go on the shower.

I'm branching off 2 22mm feeds but as a shower mixer input is 15mm I will have to reduce it.
Initially I was going to branch off with an equal 22mm and reduce to 15 near the input but as I akready have 22-15-22 reducer's I'm hoping this will be OK and not reduce pressure too much or will it?

Anyone done this or any advice?
I know it's best to have combi boiler/mains type pressure but I haven't.
Pump is last case scenario.

 

[Burnerman]

Keep the supply at 22 until the last moment, but of course its the height of the shower head to the bottom of the header tank that's important......this could be a metre or more less than the bath tap outlet.
I have 2m on my system and get an excellent shower, using a Mira system that is designed to use low pressure.
John

 

[LeeUK]

Thanks for the reply John.