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I have a vented plumbing system (cold water tank in loft and Hot water cylinder (HWC) in airing cupboard. (large one)
I have an ensuite which is 4 metres from the HWC on same floor. The hot and cold water is drawn from the cold water tank and via the HWC via a surrey flange. All pipework is 22mm copper

Prior to the impending rebuild the shower unit was fed from the Hot and cold water pipes via a Salamander twin impeller RHP75 pump (2.25bar).

The hot and cold pipework to the pump is 22mm and shortly after it, it is reduced to 15mm to the mixer shower unit. In between is two in line service ball in line valves.

Whilst the shower was okay it was not remarkable, given the pump in use.

[b]Question[/b]
[i]On the rebuild can I extend the 22mm pipework from the pump right up to the mixer unit and reduce it to 15mm to accommodate the inlet shower pipe work. (incorporating a 22mm service valves on both hot and cold pipework)[/i]
My thinking is that the 15mm pipework and the service valves are restricting the flow of hot and cold water, or is there a valid reason why 15mm pipework is used?

I have purchased a Waterford Thermostatic Mixer shower which is sequential in its use.

Any help would be greatly appreciated

Geoff

you seem to have worked it out for yourself. nothing wrong with what you want to do, in fact it would be advisable. the more of the run that can be done in 22mm the better. reduce to 15mm as close to the shower as possible.