Large bore exhaust pipe attached to Vauxhaul Novas/Astras by Chavs in the misinterpreted impression that it will make these shitty motors go faster. So called because you have to be a wanker to want to attach one.
Once the act of docking has been completed, both participants proceed to urinate while continuing to maintain said docking maneuver. this gives the appearance of a leaky pipe
Mark: Dude, lets dock like it's 1999!
Dick: No way last time we did you gave me the leaky pipe!
Mark: When you gots to pee, you gots to pee