Understanding BSP Thread Sizes

BSP thread sizes are mentioned throughout our site as these are standard thread sizes used throughout the sanitary industry.

This term stands for 'British Standard Pipe' although it is used as an international measure throughout the world.

If you have a fitting and you're not sure what size it is, this simple guide should help explain about different tap thread sizes and also help you choose the right spare part for your taps.

Most common BSP sizes

3/8", 1/2", 3/4", 1", 1.25" & 1.5"

Measuring BSP Sizes

BSP Size Diameter of the thread (mm) Typical products you might find
3/8" 15.6 Small caravan taps, European size flexitail connectors
1/2" 20.9 Shower hose, valves that screw into sink or basin taps, the rigid tails on basin taps, UK flexitail connectors
3/4" 26.4 Bath tap rigid tails, valves that fit into bath taps
1" 33.2  
1.25" 41.9 Basin wastes
1.5" 47.8 Bath & sink wastes

As an example, if you have a 1/2" quarter turn ceramic disk tap valve, the 1/2" refers to the thread on the cartridge that screws into your tap - it is this thread that will measure approx. 20.9mm across.

For further reading, we recommend the Wikepedia page.

Quick Links
Tap Valves
Waste Fittings
Flexitails & Connectors

Tap Valves and Cartridges  Sink and basin wastes  Flexitail tap connectors

Understanding Tap Nozzle Sizes

To work out which aerator or nozzle you need, compare yours to the table below to determine the correct size (sizes are approximate to be used as a guide.

Quick Links
Tap Spout Aerators/Nozzles
Tap Aerators