Vitrified clay sewer pipe is still laid today, though as a do-it-yourself homeowner you probably will not want to choose this for your sewer line replacement. Clay pipe is heavy and tricky to cut. Often, your choice of sewer pipe is dictated by what your home improvement store has on hand, and none of the major retailers carry clay pipe.
While clay pipe may seem archaic, it is a viable form of sewer pipe. One great benefit of clay pipe over plastic pipe is that it is inert, making it highly resistant to chemical degradation. Because clay sewer pipe has a porous surface, it tends to attract tree roots. Roots that impinge on clay pipe may eventually cause the pipe to crack.
Cast-iron sewer pipe, like clay pipe, is associated with older homes, yet it is still installed today. One of the best things about cast iron pipe is that it is incredibly strong. A four-inch diameter sewer pipe can withstand well over two tons of pressure per linear foot. By contrast, clay, ABS, and PVC pipe are all subject to breakage.
Cast-iron sewer pipe is heavy and difficult for a do-it-yourselfer to cut. To cut a cast-iron pipe in the ground, you need a soil pipe cutter, a specialty tool that can be rented from supply houses for a small fee.
Cast iron pipe is non-flammable. This is not an issue for below-ground installations. But should you decide to continue the cast-iron into the house, you can feel secure knowing that cast-iron pipe will not melt in a fire.