PVC won't just screw on to a clay pipe.
When you need to connect PVC to any type or size of clay pipe, it cannot be done by merely going to your local hardware store and getting the correct fittings that screw together. Instead, use what is known throughout the industry as a mission coupling. A mission coupling is just a thick rubber pipe that is secured by band clamps and uniquely suitable to join virtually any pipes together that are of different materials. Does this Spark an idea?
Instructions
1. Press the ends of the pipes together and make sure they line up properly. The diameter of each pipe must not differ more than 1/8 inch. You may need to add expanders or reducers to the PVC pipe to make the joint compatible.
2. Slide one side of the Fernco 5000 series RC mission coupling or its equivalent over the clay pipe. Position the mission coupling so that it only slides about half its length onto the pipe. Use your flat screwdriver and carefully tighten the last band clamp on the coupling, securing it to the clay pipe, turning the clamp-tightening screw in a clockwise direction. If this is an unfired clay pipe, be extra cautious so you don't shatter it.
3. Place the PVC pipe end against the opening of the coupling and carefully slide it in. Butt the ends of the PVC pipe and clay pipe together inside the coupling.
4. Push and hold the PVC pipe firmly in place. As you did on the clay pipe, tighten the last band clamp. This will keep the two pipes from separating while you continue.
5. Tighten every band clamp by first beginning on the clay side and tightening a clamp, then moving back to the PVC side to tighten a clamp. Do this by tightening a clamp on alternating sides until all the clamps are secure.
Tags: clay pipe, mission coupling, band clamp, last band, last band clamp