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[Nozza]

I am fitting a new Mira Discovery thermostatic mixer shower in the bathroom.

The hot water comes from the combination boiler.

The pipe size which connects to the valve body is 15mm. The existing hot water supply pipe under the floor boards is 22mm.

Do I need to change the 22mm pipe under the floor boards to 15mm?

Will this give me a different flow rate between the hot and cold when it gets to the shower?

Thanks

[rosebery]

Of course you do have to change the pipe size.

If the cold is in 15mm already and you've got a combination boiler then you'll have both in 15mm and both fed by mains pressure so there shouldn't be a major difference.

You can always fit a balancing valve if there is.

However, I'm confused. In you other post you talk of fitting a tank stat to your HWSC. If you've got a combi bolier how do you still have an HW cylinder?

I'm even more convinced now you need a plumber in to advise you.

And again, the proper place for this thread is in plumbing not bldg regs.

Cheers