Is my swimming pool pipe 1.5 inch or 2 inch?

One thing that always confuses swimming pool owners is the size of the pipe work on their pool. This is because pipes that are called inch and a half are nearer 2 inches when you put a tape on them. With this article we hope to clear up the confusion.

The first thing to know about the pipes used on domestic UK swimming pools is that they have not gone “European” yet. Everything is in imperial. On the continent everything is in metric and metric pipes will not fit together with imperial pipes without an adaptor. The vast bulk of existing domestic swimming pools in the UK will have been constructed using “inch and a half” pipework. Some may have been built using 2 inch but they would generally be bigger pools. Nearly all pool equipment, pumps, heaters, filters etc are made with inch and a half fittings on them. But not all. Some pumps have 2 inch fittings as standard and so need to be adapted down to inch and a half.

So you would think that if you put a tape measure on your pipes you would see the pipe line up with the 1.5 inch mark on the tape – but it doesn’t.  I have to say that we don’t know why this is! What is known industry wide as inch and half pipe is actually just over 1 and 7/8ths wide on the outside diameter and about 1 and 5/8ths on the inside diameter.

"Inch and a half" pipe is actually nearer 2 inches

If you are looking at a coupler for inch and a half pipe then the inside diameter is a fraction under 2 inches and the outside diameter is 2 and 3/8ths inches. So a typical inch and a half fitting like a 90 bend is nearly 2 and a half inches wide!

To make matters even more confusing there are two types of pipes, one white and one grey in colour. The white ones are the most commonly used and they are made from ABS material known as “Class C ABS”.  ABS stands for Acrylonitril Butadiene Styrene. The grey coloured pipe is PVC (Poly Vinyl Chloride) but you can get white PVC also. You can join ABS to PVC but you need to be careful in your choice of glue. Some glues are ABS only, some glues are PVC only and some, like the one we sell, are suitable for both ABS and PVC.