Bath 15mm or 22mm?

[mikegm]

Still finding my feet as not long qualified. Just been to price up a replacement bath. At the moment a disabled unit is there. There is also in situ a safety mixing valve. One tap has 15mm pipe, the other 22mm. The mixing valve is being removed, so back to square one. Should I be piping up in 15mm or 22mm, our indoors is 22mm,(tank fed) Thanks.
I should also point out that a combi is fitted in the adjoining bedroom (cupboard) on this upstairs job.

 

[ThatsNotPlumb]

If its an unvented cylinder & combi 15mm should be adequate enough. You'd be getting better pressure & therefore presumably a better flowrate than that of say a standard vented cylinder & cold water storage tank.

If its not a pressurised system then 22mm supplies are a must. The bath will take a week to fill if fed in 15mm on a non-pressurised system..

 

[mikegm]

Thanks for that. A lot of factors to be aware of. Sorry for being thick, how would I know/what am I looking for in a pressurised system?

 

[dextrous]

Thanks for that. A lot of factors to be aware of. Sorry for being thick, how would I know/what am I looking for in a pressurised system?

If there's no CWS then it's pressurised.