22mm or 15mm

Richieduliban87 · 10 May 2020

Let’s say I will be installing a thermostatic rain shower where the red pipe is. Would it make any positive difference to the pressure or flow if I ran a 22mm pipe from my combi boiler above down to the level of the shower? The pipe will then tee off to toilet/sink/kitchen.

Mottie · 10 May 2020

Bigger is always better for flow, isn’t it?

muggles · 10 May 2020

Mottie said:
Bigger is always better for flow, isn’t it?

Not necessarily. The waterways in a combi will be max 15mm anyway, probably smaller, so 22mm pipe is rather pointless as the boiler itself is providing the greatest flow restriction

Mottie · 10 May 2020

muggles said:
Not necessarily. The waterways in a combi will be max 15mm anyway, probably smaller, so 22mm pipe is rather pointless as the boiler itself is providing the greatest flow restriction

Ah, right. I was thinking of my old gravity fed shower.

Richieduliban87 · 10 May 2020

so that's a definite no?

oldbuffer · 10 May 2020

There would be no advantage to using 22 mm pipe. There would be a disadvantage as it would hold more cold water to be flushed out before the hot arrives.

Richieduliban87 · 10 May 2020

Thanks, appreciated.

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22mm or 15mm

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