It is an offence to possess equipment with the intention of using it to consume drugs. The use must be future use. Evidence that the equipment has been used in the past is not relevant or sufficient to prove the charge.
The prosecution must show that the equipment was illegally possessed. The law is the same as for possession—there must be knowledge and custody or control.
It is not an offence to possess a needle or syringe, whether it has been used or not. It is (technically) an offence to possess other injecting equipment, such as tourniquets, spoons, and swabs. In practice, possession of this equipment is not prosecuted.
Sale of bongs and pipes
It is an offence to sell, supply or display for sale a bong or ice pipe, or the component parts of a bong or pipe, whether or not the bong or pipe was intended to be used to administer a prohibited drug.
Source: A quick guide to drugs and alcohol, 2nd edition