Water Pipe Sizing

[Camperdown]

I am doing up a large four storey house which has one bathroom on each floor, a separate toilet plus the usual kitchen sink, dishwasher, washing machine, etc.

I am really keen to make sure that people can have showers / baths / flush toilets / run taps without having to consider if someone is in the shower elsewhere in the house. The whole plumbing system had to be ripped out and replaced. I am having the cold water mains supply increased from 22mm to the maximum allowed by the water board of 32mm.

It was my intention to run 32mm supply as a mains feed up and down the house for hot and cold water, then use 22mm for individual feeds to bath taps, etc.., and finally reduce down to 15mm for the final run to taps / washbasins / etc.

my plumber has advised that this will lose pressure because of the size of the pipe and that he intends to use the 32mm from the incoming supply to the boiler / hot water tanks only. He intends to use 28mm from the hot water tanks vertically up the house to the bathrooms, because he says this will maintain the pressure bettern.

Is this a good idea? How can I ensure that I will not affect one shower / bath with another?

Thanks & Best Regads

 

[SimonJohns]

Bs6700 has a full guide on what to size it too

If this does not meet your requirements, make the sizes bigger

 

[AWheating]

what hot water system are you fitting?

 

[Camperdown]

I have two connected mains pressurised hot water tanks heated by twin gas fired condensing boilers.