Change bath 22mm supply to 15mm?

[routabout]

I'm refitting my 1950 bathroom which has the usual 15/22 arrangement to the old bath. I shall need to replace all the pipework. I have a recent Corgi fitted Baxi combi system. Mains is just over 1/2 bar bar. I'd like to use 15mm supply for hot AND cold to my bath (obviously 22 > 15 tap connector). Hot flow from my 15mm basin and 22mm bath are identical: 6 L/m. This is a many-times-extended house with mind-numbing plumbing & electrics - the use of 15mm hot feed will simplify the re-furb.
Is ths legal? Sensible?

 

[ChrisR]

15mm Advisable from a combi - even one which is working properly, which yours isn't!
Unless your mains really IS 1/2 bar, which is hard to believe unless these's a major blockage.

6l/min should be higher. Was going to type 10 but some would be set to 8.
Pressure should overcome resistance easily - it just takes longer to fill a 22mm pipe.

 

[routabout]

Many thanks, Chris, much relieved. Mains is actually 0.5 - 0.6 consistently - we're V rural and hesitate to call waterboard as improvement will be at our expense and I'm fearful of being "shut down" in the waterworld equivalent of unsafe gas or electrics.