BSP Fitting Sizes

We often have customers who are unsure of how to correctly measure their fittings to find their BSP Fitting Sizes, so here is a useful guide to help.

Understanding BSP Sizes and Measurements

When measuring BSP (British Standard Pipe) sizes using a ruler, you might notice that the numbers don’t quite match your expectations. For instance, a 1/2 inch BSP thread may appear closer to 3/4 inch when measured with a ruler.

This discrepancy stems from the original sizing method. BSP sizes were initially determined based on the inside diameter of a steel pipe, measured in inches, for which the thread was designed. However, it’s important to note that these numbers do not refer to the outside diameter of the male thread.

There are two primary types of BSP threads:

1. Parallel Threads (BSPP): These threads run in a straight line and are often designated with the letter G. For example, G 1/2″ represents a parallel 1/2 inch BSP thread.
2. Taper Threads (BSPT): Taper threads gradually narrow towards the end and are sometimes labeled with the letter R. For instance, R 1/2″ indicates a taper 1/2 inch BSP thread.

To add a bit more complexity, the ‘T’ in BSPT can sometimes refer to ‘Thread’ without specifying whether it’s Taper or Parallel.

How to Measure your Outdoor Tap

If your outside tap does not already have a quick-click attachment pre-installed, purchase an Outdoor Tap Connector. Most outdoor taps feature a 1/2″ or 3/4″ outlet but it is worth measuring to get the correct size. To measure, take a ruler to the outside thread and note down the width between both widest points. If your tap, for example, is measuring 1″ then minus 1⁄4″ of an inch to get the size of connector required. In this case, that would be a 3⁄4″ Tap Connector