3/4 and 1/2 inch connections - shower mixers

[questaqui]

I am so confused! I don't know anything about plumbing!

I am re-doing my bathroom and intend to have a bath with a fixed head shower and a hand held shower. I will have a thermostatic mixer to 3 outlets (2 showers and bath overflow filler). I will also have a pump.

I am told that one should have a thermostatic mixer with 3/4 inch connections as this gives a better flow rate. But then I have been looking at fixed head showers and they all seem to have 1/2 inch connections. The same companies that do 3/4 inch mixers then have 1/2 inch heads - why is that?

Also, if one has a mixer with 3/4 inch connections, what happens if the pipe from the water cylinder in 1/2 inch? Does the pipework need to be changed, and is that an expensive job?

What's it all about?! I seem to be totally unable to get to the bottom of this story. Any advice would be so gratefully received.

 

[newbuildinstaller]

if you have high pressure system (combi/unvented) 15mm pipework to the shower is fine 22mm would be better but 15mm will work.

You need 15mmx3/4" male irons. And a 1/2" fixed head is adequate a 3/4" would be giant

 

[muggles]

You need ¾" from your cylinder and loft tank to the mixer, and probably ¾" (22mm, more correctly) from the mixer to the bath filler as well, but ½" (15mm) to the shower