Domestic cold water system

[mos65]

I am renovating my house at the moment & this involves a total re-plumb.
I understand that the cold water supply should start off from the mains at 22 or 28mm dia and reduce in size as it gets further down the line & varoius appliances tee off.
My question is, is this still worth doing when the supply into the premises is only 15mm? Basically our house was built in the 70's by the previous owner, & it seems that the mcw supply he put in is just a 15mm copper pipe which comes up through the garage floor & in to the meter.

 

[moggridgeplumbing]

If you only have 15mm incoming it will be pointless to change to 22mm. Run the lot in 15mm.

If you have any downwater services from a cold water tank then you will get the benefit of starting in 28/22mm from the tank.

 

[twgas]

I'd use the bigger pipe, if in the future you decide or need to replace the main you could upgrade and get a real benefit.