size of pipe for gravity-fed shower

[stevewilliams]

I've just had my cylinder moved to an upstairs bathroom and noticed that the plumber has changed my gravity fed shower downstairs from 22mm to 15mm pipe. Surely 22mm is a minimum requirement for a gravity fed shower?

 

[seco services]

no why would 22mm be a min requirement ?
does it work ?

 

[stevewilliams]

It works but the flow seems reduced. Surely the flow rate is reduced if the pipe volume has been reduced by 50%?

Doesn't this mean I'm getting less water through in a given time?

 

[stevewilliams]

.....and surely the bath should still be 22mm?