Main pressure water sizing

[Inverness]

if I have a prv already on my water main supply as it's great pressure. Would there be much difference if I installed a 32mm alkathene pipe compared to 25mm alkathene pipe?

 

[ShaunCorbs]

You would only increase the flow rate if this is already good no point

Do you know your flow rate?

 

[kozak1968]

If you have an unvented system which probably works at 3 bar then a 25mm supply would be adequate. But if you have high static pressure may not mean you have good dynamic pressure, which is what counts. You need to test the flow rate.

 

[Inverness]

Prv on the incoming supply and before it goes into the unvented cylinder there is another one set at 3 bar.

 

[Inverness]

Atm the supply water main feeds four houses on 25mm alkathene. But with my new water main I'll be connected onto the the 3" watermain which is less 25metes away only for my house.

 

[kozak1968]

Installing a 32mm blue poly ( maybe alkathene in Scotland) is good if the water suppliers main is a long way from the property but usually not needed on average size properties. You need to test the flow rate.

 

[Inverness]

Ok I'll test the flow rate. There's a prv on the incoming main.

 

[Inverness]

I think rule if thumb if your water main is further than 40 meters then 32mm supply pipe with be correct size.

 

[kozak1968]

Recommended minimum for an unvented cylinder is 1.5 bar and 20 litre per minute flow rate for one bathroom. If you have more bath /showers then you would require more. If you scan the internet you will find some calculations to help you.