Bath Tap pipework.

[Arthur]

Is it acceptable to have 15mm pipes and fittings all the way up to a 15mm - 22mm reducer (in this case biggerer..er!) that will be perhaps an inch below the 22mm flexi hoses?

thanks for your advice.

Arthur.

[Set Square]

How do you define "acceptable"? As far as I know, there's no *law* against it. Depending on how much pressure you've got (mains or gravity?) and how fast you want your bath filled, it may or may not be acceptable to *you*. I have to say that it is *usual* to have at least the hot feed to the bath in

22mm pipe.

[chris French]

In message , Set Square writes

For a tank fed system, for say a combi at mains pressure then 15mm is enough (the restriction is the boiler not the pipe.)

[Arthur]

Thanks, Set Square. Having since consulted 'Collins', it says I should put 22mm feeds to both H & C. However, since the new Combi has a 15mm mains inlet and outlet to Hot taps. At which point does

15mm become 22mm?

The Combi will be installed in the bathroom and so as the 15mm mains emerges from the kitchen below into the 1st tee-fitting it will feed the bath cold tap (also electric shower and cistern) on the way to the Combi. The other side of the 1st tee will feed the wash basin.

Are there any extenuating circumstances here?

Arthur.

[Set Square]

The fact that you are heating your water with a combi means that it is at mains pressure - so 15mm pipe can probably deliver hot water as fast as the combi is able to heat it. [That may not be fast enough to fill a bath quickly - but the "bottle-beck" is in the combi, not in the pipe].

22mm would be necessary if you had a hot water cylinder, and a cold header tank in the attic - but you don't - so 15mm is ok.

[Arthur]

Thanks, Chris. This also answers my follow up question to Set Square. I should have mentioned the Combi in my orig post.

Arthur.

[Arthur]

Thanks again, Set Square.