If you are installing a PVC home water system pipeline to a sewer main line made of clay pipe, a special coupling is required. In most cases, all sewer main lines owned by the water company are already fitted with the proper y-fittings. All you need to do is connect the PVC pipe to these fittings. You should do this under the supervision of a certified plumbing and sewer expert from the water company. You also must have the proper-sized PVC pipe to match the sewer connection.
Measure the diameter of the connector on the end of the sewer line. Make sure it is exactly the same size as the PVC pipe you are using. If not, you will need to size and buy an adaptor to connect the pipes. One end must match the diameter of the sewer pipe connector; the other must match the diameter of your PVC pipeline.
Loosen the steel clamp using a large slot-head screw driver on one end of the Fernco coupler.
Slide the end of the coupler over the PVC pipe so there are 5 to 7.5 cm (2 to 3 inches) of coupler over the pipe walls. Using a large slot-head screwdriver, tighten the clamp.
Loosen the other clamp with a slot-head screwdriver. Slide it over the sewer pipe. Again, there needs to be at least 7.5 cm (3 inches) or more of coupler over the pipe walls.
Test the clamp tightness by inserting a torque wrench with slot-head into the clamp screw head and turning the wrench. It must be tightened to 6.8 nm (60 inch pounds) of torque.