Pipe sizes for bath/basin water

[markwm]

Re-doing a bathroom with combi boiler installed already.

The hot bath tap is supplied by 22m pipe, this then splits with a Tee to 15mm to go to the basin hot.

The cold bath is 15mm and so is the cold basin.

I have a couple questions:

1: Is the bath hot supply 22mm for a reason? I'm replacing the taps and moving the bath so the pipework will be changed, do I still need to keep the supply to the bath hot tap 22m or can I safely use 15mm and 15mm to 3/4" tap connectors?

2: I'm also installing a manual mixer shower. Is it fine to use 15mm runs to it or should again the hot be 22mm?

 

[Softus]

1: Is the bath hot supply 22mm for a reason?

Yes. It provides a flow rate more suitable for drawing a bath of hot water before it goes cold.

I'm replacing the taps and moving the bath so the pipework will be changed, do I still need to keep the supply to the bath hot tap 22m or can I safely use 15mm and 15mm to 3/4" tap connectors?

2: I'm also installing a manual mixer shower. Is it fine to use 15mm runs to it or should again the hot be 22mm?

You should use what the boiler manufacturer stipulates.

 

[kevplumb]

1: Is the bath hot supply 22mm for a reason? I'm replacing the taps and moving the bath so the pipework will be changed, do I still need to keep the supply to the bath hot tap 22m or can I safely use 15mm and 15mm to 3/4" tap connectors?

from the days when you had tank fed hot water

2: I'm also installing a manual mixer shower. Is it fine to use 15mm runs to it or should again the hot be 22mm?

15 will do the flowrate from a combi dosen't need 22 normally