Pipe Sizing Guide

PLEASE NOTE: These fittings are imperial (inch) IPS (Iron Pipe Size / Internal Pipe Size) sized and NOT metric(mm). There is a difference.

When measuring pipe we use the Outer Diameter of the pipe, which will fit into a ‘socket’ fitting, which could be an elbow or a valve for example.

The size of the fitting is classified by the internal diameter of a pipe and not the fitting itself. ie. A 1″ corner piece will fit a pipe of an internal diameter of 1″, but the actual 1″ fittings’ size itself, would be deceptively much larger.

All PVC fittings are of industry standard water pipe type (except perspex) – cheap, proven, reliable, reasonably easily available and internationally certified

Please remember that the fittings are designed for US Imperial sized pipe because the market is enormous in the US and these fittings are very popular there. These fittings will not fit Metric sized pipe or any pipe that has metric sizing printed on it, even if printing on pipe makes mention of Imperial measurements as well as metric – if it makes any mention of mm’s it won’t fit in the fittings due to international standards variances.

If you wish to use Metric sized pipe, it can be done, but, you will need to either chamfer down the diameter of the pipe slightly or increase the girth/width by glueing a thin piece of PVC or Styrene sheet around the pipe so it fits snugly into the fittings.
The most commonly available pipe sizes in the UK are 1 1/2″ (One and a Half Inches) and 2″ (Two Inches) – Mainly used in the Swimming Pool industry.

To guarantee correct sizing and pipe compatibility we recommend obtaining your pipe from IPS flow systems (UK based).
Please visit this direct link to order your required pipe size which will fit the connectors that we sell.

Imperial Size Chart

Imperial Pipe Sizes 

 Pipe Size  Outer Diameter of PipeInner Diameter of Fitting
1/2 Inch21.4mm 21.4mm
3/4 Inch 26.5mm 26.5mm
1 Inch 33.6mm 33.6mm
1 1/4 Inch 42.2mm 42.2mm
1 1/2 Inch 48.3mm 48.3mm
2 Inch60.3mm 60.3mm

Use this image to get an idea of scale – the hand in the pictures below is that of an average adult male: