Hose size guide

Silicone hoses are sold by their internal diameter (ID), which is the size of the hole through the middle. Getting the ID right is what gives you a tight, leak-free joint.

1. Measure the pipe, not the old hose

Measure the outside diameter of the pipe, spigot or outlet the hose will push onto, using vernier callipers if you have them. That measurement is the hose ID you need. For example, a pipe that measures 25mm across the outside takes a 25mm ID hose.

Old hoses stretch and go out of shape, so measuring an old hose can give you the wrong size.

2. Joining two different sizes?

A straight coupler joins two pipes of the same size. If the two pipes measure differently, you'll need a reducer instead.

3. Pick hose clips to suit the outside diameter (OD)

Hose clips go around the outside of the hose, so size them using the hose's outside diameter rather than its ID.

OD = ID + (2 × wall thickness). For example, a 25mm ID hose with a 4.5mm wall has an OD of 25 + 9 = 34mm, so choose a clip whose range covers 34mm. The OD and wall thickness are listed in the spec table on every product page.

4. Length

Allow enough length for each pipe to go well inside the hose, with room for a clip behind the pipe's bead or lip. Straight lengths can be cut down to size, so if you're unsure, go slightly longer and cut square with a sharp blade.