Tugging your meat until you ejaculate, and then pissing. This supposedly cleans your urethra (hence, Cleaning the Pipes)
It stings, and that's evidence that it's doing what its name says.
It can also be done right before having sexual intercourse, so you don't get a woman pregnant, and you don't have to wear a condom.
John: "Ugh, I really need to clean the pipes"
John is Cleaning the Pipes in Cindy's bathroom so he can smash her, rawdog.
Anglo-American slang term used to describe the act of mastubation in order to empty one's testicles of a thick, fat, juicy load of baby-batter in order to start a newer batch.
Or, in the case of the film 'There's Something About Mary,' the theory that "cleaning your pipes" will steady your nerves before a date because your body will not think you are trying to have sex because you will have tricked it into thinking you have done already...
"Percy spent two hours cleaning his pipes because he hadn't shot his load for four days."
"Hey Gordon, you should clean your pipes before seeing Jennifer tonight, it'll steady your nerves."
Afta cumming have a piss to clean the pips
afta macking a hot chick or wanking, go have a piss. cleaning the pipes
Cleaning the pipes basically means after you have had a wank you go to the toilet to "clean the pipes" as it were, also useful to prevent willy dribble
I was going to see my girlfriend but I had had a wank so I had to make sure that I did a thorough job of cleaning the pipes to make sure that there wasn't any willy dribble, especially for the fact I was wearing shorts to make sure that I would stay breezy in my high riding breezy shorts in the summer.