Step 7 · Measure and Cut the PVC Pipe

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.

Measure the exact distance between the two ends of the cast iron pipe. From this measurement, subtract the 'insertion depth' required by the shielded couplings (this accounts for the small gap the pipe ends sit within the coupling). This final number is the required length of your new PVC pipe. Use a PVC pipe cutter or a hacksaw to cut a piece of Schedule 40 PVC pipe to this precise length.