What Pipe Diameters to use for Hot and Cold Supply All aspects of plumbing questions and answers, help, tips and information

[HCross]

Hi Everyone,
I'm new to posting in this forum although I have often used it for loss of tips with previous projects.
My situation is this...
I'm redoing my water pipes in my flat which has a 15mm cold feed in.
I have a combi boiler.
I'm putting in pex piping like for underfloor heating as I'm in Hungary and it's standard.
It's a small flat, so total of 2 sinks, loo and bath/shower.
What diameter pipes should I use for my cold and hot?
I was thinking of either
1... 16mm throughout
2... 22mm from cold feed to combi with 16mm branches for appliances
And hot all in 16mm
Please shoot me down if appropriate.

Thanks
HC

[Barbastelle]

This is an interesting question. I do not know your pipe size in Hungary but with a combination boiler in the UK 15 mm should be fine for the hot and cold as the water to the boiler will be pressurised as so the same as to your cold taps.