Step 9 · Install the PVC Pipe
Take your pre-cut piece of PVC pipe. Insert one end of the PVC pipe into one of the couplings already on the cast iron pipe, pushing it until it hits the internal pipe stop. Now, slide the second coupling from its position on the cast iron pipe over the other end of the PVC pipe until it is centered over the joint. Ensure both ends of the PVC pipe are fully seated inside their respective couplings.