Tie In to Cast-Iron Pipe With PVC
Mastered in a Minute: No-hub couplings make it easy to tie in to existing cast-iron drain/waste/vent lines with new PVC.
Tying in to cast iron with PVC is a great way to add new waste lines.
First, fabricate your PVC wye fitting. Using a regular wye, cut two lengths of PVC that will slip into the ends of the wye fitting and hold the no-hub fittings that attach the PVC to the cast iron.
Measure the length of the assembly, and add 1/4 in. Then mark that length on the cast iron with pencil lines, and use zip ties to mark the cut on the pipe.
Use a reciprocating saw with a metal-cutting blade rated for cast iron to make the cut. Seat the saw’s shoe against the pipe, line the blade up with the mark, and begin sawing. Keeping the saw’s shoe in contact with the pipe helps keep the blade square to the cut, and reduces vibration and the chance of kickback. Don’t force the cut; let the tool do the work.
Once cut, wipe the pipe with a rag to remove debris, and use a file to remove any burrs.
To make the connection, use no-hub couplings rated for your type of pipe. The ones used here are designed to transition from regular cast iron to PVC or extra-heavy cast iron.
Remove the stainless-steel outer banding from the coupling’s neoprene gaskets, slide the gaskets onto each end of the PVC fitting assembly (making sure that the gasket is oriented properly; each end has a slightly different diameter), and fold it back on itself. Then align the fitting assembly with the cast iron, unfold the gaskets over onto the cast iron, and slip the bands over the gaskets.
Finally, tighten down the nuts using a ratcheting torque wrench, and the transition is complete.