Define Complete The Circuit Meaning

(flush)
Phil: "Dude, you were in there forever! Did you just drop a deuce?"
Mike: "No, but I appreciate your interest in my bowel activity. I decided to take my 40 of Bud in there with me and complete the circuit. That shit is just like water - goes right through you. I must have been pissing for a solid 3 minutes without stopping!"
Phil: "Like water? Buttwiper pretty much IS water! Why are you drinking that horse piss instead of this awesome 90 Minute I've got?"
Mike: "Bad economy, man."

"So there I was, balls deep, and she just decided to try completing the circuit while i was doing him"

Chad: “Kelly and I tried completing the circuit last night.”
Brad: “That’s wife material right there.”