Step 4 · Clean the Existing Pipe Ends

This is the step people usually slow down on. Go finger-tight first, then a quarter turn. No rush — replay the clip whenever it helps.

For the new flexible couplings to create a perfect seal, the ends of the remaining cast iron pipe must be clean and smooth. Use a heavy-duty wire brush to scrub the outside surface of both pipe ends, removing all loose rust, scale, and grime. If there are any significant burrs or high spots left from the cutting process, use a metal file to smooth them down. The goal is a clean, uniform surface approximately 2-3 inches from the end of each pipe, where the rubber gasket of the coupling will sit.