The 15,25,30,55 and 75watt models come supplied with 1.5" hosetails, you can also hard plumb using 1.5" BSP male fittings. You can find these fittings at the following links
single-union-threaded-male-to-plain-female
converter-threaded-male-to-plain-female
If you are plumbing to black pipe from a plumbers you will need adapters which you can find here
reducing-sleeves-imperial-pressure-to-waste-pipe
The 110watt professional UV has no fittings supplied. It requires 2" solvent weld pressure pipe which can adjusted to suit your personnel requirements.