Before beginning any work, put on your safety glasses and heavy-duty work gloves to protect against sharp metal fragments and dust. Clear the area around the cast iron hub of any obstacles to ensure you have adequate space to work safely and effectively.

This is the most critical and labor-intensive step. Use a hammer and a cold chisel to carefully break up the old lead seal inside the hub. Place the chisel against the lead and strike it firmly to fracture it. Work your way around the pipe circumference. An alternative is to drill a series of small, closely spaced holes into the lead using a drill and a metal bit, which will weaken it for easier removal. Once the lead ring is broken and removed, use a pair of pliers or a large screwdriver to pry and pull out the old, packed oakum (a tarred, fibrous rope) from underneath the lead.

Once the bulk of the lead and oakum is removed, a thorough cleaning is necessary. Use a wire brush to scour the inside surface of the cast iron hub. For best results, use a wire cup brush attached to a power drill. This will efficiently remove any remaining lead fragments, rust, and debris. The goal is to create a clean, smooth surface for the new gasket to seal against. After brushing, wipe the inside of the hub clean with a dry rag.

Measure and cut your PVC pipe to the desired length using a PVC pipe cutter for a clean cut, or a hacksaw. After cutting, it's very important to prepare the end of the pipe. Using a deburring tool or a simple utility knife, carefully shave the sharp outer edge of the pipe to create a slight bevel or chamfer. This bevel will allow the pipe to slide into the rubber gasket without catching, tearing, or folding it over.

Take the rubber 'donut' gasket and apply a liberal amount of plumber's grease or a thick soap and water solution to its entire outer surface. Also, apply lubricant to the clean inner surface of the cast iron hub. To install, fold the gasket slightly (like a taco) to get it started in the hub opening. Then, using firm and even pressure with your thumbs, press the gasket into the hub until its outer flange sits flush against the face of the hub. Ensure the gasket is not twisted inside the hub.

Apply plumber's grease or soapy water to the beveled end of the PVC pipe and to the inside surface of the installed donut gasket. Align the pipe with the center of the gasket. Using a firm, steady pushing and slight twisting motion, force the pipe into the gasket. The bevel should help guide it in. Push the pipe until it stops against the internal shoulder deep inside the hub. If it is difficult to push by hand, you can place a block of scrap wood on the other end of the pipe and gently tap it with a mallet to drive it home. Ensure the pipe is inserted straight and fully.

The final step is to verify your work. Run a significant amount of water through the newly connected drain line. A bucket of water or flushing an upstream toilet multiple times works well. While the water is flowing, carefully inspect the connection point where the PVC enters the cast iron hub. Look and feel for any signs of moisture or dripping. If any leak is detected, the pipe may need to be removed and reseated.