showwer feed and pipe diameters

[shouldknowbetter]

I am planning to install a shower into a new extension. The supplies will be mains CW, gravity HW. I have read other posts about using single pumps and pressure equalising valves to balance the supplies. The HW feed to the pump will be as a branch from the supply to the kitchen. It is currently 15mm copper pipe, and the new feed will be plastic. After the branch I will fit a check valve to prevent siphonage from the kitchen sink. Is 15mm sufficient to feed to the pump,
and from the pump should I then run 15mm or 22mm to the mixer,
and then 22mm from mixer to shower head. (Yet to buy pump, valves, mixer and shower head.)

Any advice greatly appreciated

 

[grrinc]

I doubt you will find a good pump that can be pumped from the feed to the kitchen tap. Pumps need to be supplied direct from hot water cylinder ( via a sussex or surry flange ) or they can be the first draw off off of the top of the cylinder. To tee off from so far down the line will result in air intake that will knacker your pump in no time.

Should you wish to proceed anyway ( you shouldn't ) then keeping it all in 15 will suffice.

 

[shouldknowbetter]

OK thanks, comments noted.

I've now bought the shower mixer valve and the fittings are 22mm.

The cold mains feed is 15mm and I'll increase the size to 22mm at the mixer. For the hot, can I run 15mm from the tank to the pump and pump to mixer, increasing to 22mm there, or should I get a 22mm pump, and run that the whole length?

Cheers