Stern Lecture Plumbing is a business located in Springfield, whose business slogan (as seen on the truck) is "I told you not to flush that."
Homer called Stern Lecture Plumbing when a pipe in his basement sprang a leak, flooding the basement with a foot of water and trapping Snowball II, much to Marge's concern. The plumber said it would take two or three weeks to get the parts he needed to fix the leak—and that was if he ordered the parts the same day, which he said he wasn't going to do. The unnamed plumber's pager then started beeping, and the message on it was "LOW BATTERY." Saying he had an emergency call, he left and said that until he came back, they could just put a pan in the basement. Homer tried it and the pan floated away, angering Homer and prompting him to add Stern Lecture Plumbing to his Revenge List.
It later turned out the plumber was a member of the Stonecutters and would only give preferential treatment to his fellow Stonecutter members free of charge. After Homer joined the Stonecutters, Stern Lecture made a return visit to the Simpson basement. At first, the plumber tried to give Homer another brush-off, saying he never got around to ordering the parts and it would still be a couple of weeks before he could fix the leak. However, things changed quickly after Homer identified the plumber as a Stonecutter (by exchanging the secret handshake and showing their Stonecutter T-shirts). Realizing that Homer is a new member, the plumber happily changes his tunes and instantly fixes the leak with a pipe wrench before rescuing a sputtering-but-safe Snowball II, much to Homer's delight.