What size hot and cold water distribution pipes 22mm or 28mm | Bathroom Advice | Plumbers Forums

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S

sdsparks

So I have to install new hot and cold distribution system to large house with 1 main bathroom (Shower, Bath, Basin, WC), 2 on-suites (shower, basin & WC) , 1 cloakroom WC ( Basin & WC), 1 kitchen.

I have a 1 inch main and good pressure

The plan is to install a megaflow then distribute H&C around house in 22mm then branch of in 15 to appliances (Basin taps, WC, Shower etc) expect in 22mm to bath.

My question is, is 22mm big enough for H&C distribution or should I go to 28mm?

Thanks

Sam
 
http://www.ukcopperboard.co.uk/literature/pdfs/Installation-Tips/Pipe-sizing-tabulation-method.pdf

if the bath is a normal sized bath then i would run 15mm hot and cold, 22mm would possibly cause a drop in flow to other fixtures if the bath taps were fully open (dependant of supply). Id also consider 10mm to basins for simular reasons. Seem this done on hundreds of new build houses and worked very well. If you do not have a great dynamic pressure and flow rate on the main then fitting flow restrictors can also help.
 
As your normal Megaflow has a 22mm inlet & outlet, there's not a lot of point using anything other than 22 to distribute from the cylinder for both hot & cold (assuming you're balancing the hot & cold at the combi valve). I might consider getting a 28mm combi valve & supplying it with the 1", then reducing to 22 after the valve, to squeeze the max out of your cold main.

Yes, 22mm to the bath & 15mm elsewhere, but what size inlets do the showers have, 22 or 15mm? Supply them accordingly.

Have fun!
 

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