25mm supply - 28mm mains

6 Aug 2004
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United Kingdom
I have a new 4 bed house which has a 25mm MDPE water supply pipe installed. Everybody told me, including the water board, that 25mm was sufficient for a 4 bed house. A plumber quoting to install the system has suggested that a rising mains pipe of 28mm be used, then distribute with 22mm pipes. He says that, if I do not want to change the supply pipe to 32mm, the 25mm may be adequate. The system will have mains pressure supply to outlets. No water tanks in the roof. The water company supply is 3 bar.

My question is, does it make sense then to have the 28mm rising mains pipe, as opposed to 22mm if I leave the 25mm supply? is there a benefit in my system?
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It depends what the flowrate is coming up the road, as usual.

I would agree with a 28 mm rising main.

However, with mains supplied hot and cold its normal to distribute in 15 mm to the individual outlets.

If its being done in ( dreadful ) plastic tube then a very good way is to have a manifold on each floor and individual 15 mm pipes to each outlet.

The distribution is 28mm mains >22mm branches >15mm to taps etc. yes, in platic tube with manifolds.

On the flow rate, will the water company tell you what the flow rate is or do I have to work it out
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It can unle be measured as it mostly related to the pipe coming into the house from the street.

Bit too late to change your design now!


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