Rising main sizing - 15mm or 22mm

[jesteh]

My rising main comes into the house from the cloakroom in 25mm MDPE pipe (which is brand new all the way to road).

From rising main its around 5m length of pipe to the boiler with tees to 3 sinks, 3 toilets, a bath and a shower. All the tees are before pipe gets to the boiler.

My plumber wants to put the 15mm pipe in from rising main to the boiler as the boiler only accepts 15mm feed so he thinks it'll be sufficient.

Is he right or would it be better to put in 22mm?

 

[Jordon]

22 as far as you can then a pressure reducing valve to control the pressure in to the boiler

 

[oss]

With quite a few things liable to be used at the same time I would put 22mm in.The size of the pipe affects the flowrate not the pressure ie with 22mm, run a couple of appliances you probably would not notice the difference at the taps ect with 15 mm you would.Unless you have very high pressure in the incoming mains i can,t see the need for a pressure reducing valve.

 

[Jordon]

Just common practice I use as if it has a new main and the flow rate is at 20ltrs a min at 1.5bar then the water board fix a faulty line and the flow rate and pressure pick up you can get caught out also helps to get equal pressures.

 

[carlramsay]

22 as far as you can then reduce