How do I know what size water pipe I have?

All you need to do is wrap a string or a flexible tape measure around the outside of the pipe. Now, take this measurement and divide it by pi (pi = 3.1415). This calculation is the plumbing pipe’s Outside Diameter that you can use to look up the Nominal Size.

What size should water pipes be?

In most cases, the main pipeline from the street to your home is either 3/4 or 1 inch in diameter, supply branches use 3/4-inch-diameter pipe, and pipes for individual components are 1/2 inch. Remember that water pressure decreases by a half-pound per square inch for every foot pipes extend above your water supply.

What is NPS valve size?

Nominal pipe size (NPS) is a dimensionless designator of pipe size. It indicates standard pipe size when followed by the specific size designation number without an inch symbol. For example, NPS 6 indicates a pipe whose outside diameter is 168.3 mm.

What size are standard water pipes UK?

In UK domestic plumbing the sizes commonly found are 8mm, 10mm, 15mm, 22mm, 28mm, 32mm, 40mm, 50mm, 68mm and 110mm; with sizes up to 28mm being used for hot and cold water supply, heating and gas supply, and larger sizes for waste, rainwater, soil and ventilation.

How do you determine your fitting size?

Quote from the video:
Quote from Youtube video: So this is right about one inch on the outside there you take off a quarter. From one inch that gives you three quarters.

What are the different sizes of plumbing pipes?

1. PVC Pipe Sizes

NPS Outside diameter of pipe (inch) Inside diameter (inch)
3/8” 0.675” 0.493”
1/2” 0.840” 0.622”
3/4” 1.050” 0.824”
1” 1.315” 1.049”

What size water pipe should I use in my house UK?

a new or replacement connection



The standard service pipe size for domestic purposes is normally 25mm (outside diameter). However, in exceptional circumstances a domestic service could be up to 63mm (outside diameter).

What size is normal house water pipe?

Mains should be in 15mm.

What size incoming water main do I need?

Connection size



For most domestic properties a standard 25mm or 32mm connection will be sufficient. For larger commercial properties you may require a bigger supply – this will be based on the fittings e.g. toilets, basins, showers etc you’re planning on installing in the property.

What size is blue mains water pipe?

In the UK 25mm MDPE is the standard size of new water supply pipe for a domestic property, and if less than 40m of continuous below ground water supply pipe is needed, however check with local water authority requirements for your project as certain areas may differ. 12.5 bar maximum operating pressure.

Can you go from 15mm to 22mm?

2 Answers from MyBuilder Plumbers



Save yourself the cost and use 15mm because: – flow rate is improved through 22mm because the bends (and pipework) have a lower frictional resistance so unless it’s a very long, bendy run there will be no improvement.