Twin Headed Shower Fed By 22mm or 15mm?????

[monkeysDIY]

I'll start with sorry as Im sure its been asked before.
Adding a twin shower off bath tapp feeds. They are fed by hot and cold 22mm. Now system is off a combi fed by 15mm also. What will happen to pressure if I use 22m (lower or increase flow) and again if I use 15mm???

Thanks for assistance

 

[monkeysDIY]

Sorry. Can I just take a 3 way T-Piece 22x22x15 off bath tapp pipe. Will this do to performance.......

 

[gigz]

Just use 15mm supplies to the shower, no problem. Did you check the shower is compatible with a combi ? (a lot aren't) Also fit isolation valves to shower pipes.