Plumbing house in 22mm

Artrax · 28 Nov 2020

Morning All,

So I'm going to be completely replumbing my house in the very near future due to a rearrangement of the internal layout (with the addition of an extra bathroom.)

I just wondered if there was any benefit at all in doing it in all 22mm pipe rather than 15mm?

The mains supply comes up through the screed at 15mm. No idea what it is underground. I get 20l/m at 5.2 bar and whilst I know it won't magically increase the flow, I'm thinking it might make a little bit of difference if I have multiple outlets open at the same time?

If anything I'm hoping that this will reduce the noise of water flowing through the pipe...

Thanks

ianmcd · 28 Nov 2020

what are you using for your HW ? a combi boiler , unvented Cylinder ?

Artrax · 28 Nov 2020

At the moment, vented cylinder, but that's being taken out.

Not sure yet what I'm replacing it with (combi or unvented.) I had another post on here asking if unvented was viable and the answer seemed to be yes, so most likely that.

Thanks

Nozzle · 28 Nov 2020

If your hot water pipes are 22mm, you have to draw off more (twice as much) cold water before it comes warm/hot. And therefore it costs you more in gas/leccy, and to a lesser extent, water

Nozzle

Artrax · 28 Nov 2020

That makes sense re the hot water. Leave that as 15mm then?

What about the cold? Any benefit to doing this in 22mm? Even if to reduce noise (I'm assuming it would, though by how much I'm unsure.)

Madrab · 28 Nov 2020

Artrax said:
The mains supply comes up through the screed at 15mm

That's your bottleneck, 15mm will flow less at a given pressure than 22mm will. That's where you need to look at first before changing the rest to 22mm. I assume you will have a bit of water noise too as the 15mm water velocity will be quite high.

Your pressure is quite high too, that can cause issue/stress with certain valves and outlets. Ideally you would fit a pressure reducing valve and crank it down to 3 bar.

Artrax · 28 Nov 2020

So assuming that the mains into the house was upgraded (something I was considering for the future), then would feeds to all the cold outlets benefit from 22mm?

I do have a fair bit of noise, that's why I'm exploring replumbing in 22mm even if I won't see any improvement in flow rate, although I'm guessing it might 'future proof' too for if/when I change the mains supply pipe...

Will look into a pressure reducing valve. I think I would need one with an unvented cylinder anyway.

Thanks for everyone's input!

muggles · 28 Nov 2020

Yes, I think in your situation a re-pipe in 22mm would be beneficial, assuming you're going to get your mains upgraded. While you're at it, run a new main up to the cylinder cupboard from wherever your new main stopcock will be, then distribute the rest of your cold from the cylinder cupboard to the rest of the house. Doing this will allow your cold to be fed through the same pressure reducing valve as the cylinder, keeping the pressures equal for best performance

Artrax · 28 Nov 2020

Great thanks, that sounds like a plan.

A further qestion about upgrading the mains... Would that have to come from outside through the foundations, and rise inside the house, or can it rise up outside (insulated) and come through the wall above ground/floor level?

Just wondering if I'll need to dig my floor or not, and get this done before I put a finished floor in.

muggles · 28 Nov 2020

Better to duct it through the foundations to inside if you have the opportunity to do so.

Artrax · 28 Nov 2020

Darn it. I figured that was the best option I just didn't really want to dig the floor up.

Thank you.

Madrab · 29 Nov 2020

You do get a product designed specifically for your situation, it's called insuduct - groundbreaker.

https://groundbreaker.co.uk/products/insuduct/

It allows an insulated external water pipe to be run up the outside wall and then into the hose and avoids breaking into concrete floors.

Of course bringing it in through a duct, under the floor, is the traditional way to go.

Bullet-Proof_Biscuit · 7 Dec 2020

If you're going to install a new house supply from the utility valve then definitely run that in 32mm MDPE rather than 25 which they'll probably suggest (it's only a bit more dear).
And piping it under the foundations will be neater - less external pipes the better imho.

Artrax · 7 Dec 2020

Thanks. Nice to know there is a product that would allow an external installation but you're both right - if I'm going to do it then I should do a proper job!

Bullet-Proof_Biscuit · 7 Dec 2020

There was a YT video about it I watched recently by 'the restoration couple', core drilled & ducted new 32 mdpe into kitchen from the street. Worth a watch along wit their other vids

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Plumbing house in 22mm

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