Most sprinklers have a 15mm or 20mm female thread at the inlet of the sprinkler. For most people who aren’t familiar with thread sizes, it’s easy to assume that measuring the thread with a ruler will indicate the size of the fittings needed. Unfortunately doing this will result in ordering fittings that are not the correct size (usually too big). If you have a fitting or pipe that you need fittings for, manufacturers will usually have the size printed, stickered or embossed on the fitting itself. That’s a guaranteed way to know what size fittings you need. If you are unable to find any markings, the information below will help you select the right size fitting or pipe you need!

In Australia the naming convention for thread sizes follows the BSP (British Standard Pipe) standard. There are male (BSPM) and female (BSPF) threads. BSP threads and PVC Pipe have nominal sizes, meaning they are only called ’15mm’ or ’20mm’, but do not actually measure to that size. offers a range of fittings range from 15mm to 80mm with BSP thread sizes. Sometimes these fittings may be referred to in imperial form. For threads and PVC Pipe: half inch refers to 15mm, three quarter inch refers to 20mm, one inch refers to 25mm, one and a quarter inch refers to 32mm, one and a half inch refers to 40mm, two inch refers to 50mm.

To find out what size threaded fitting you have, measure the outer diameter of male threads and inner diameter of female fittings.