Sewer lines, in older homes, can be made of lead, clay or cast iron. Code dictates that new home sewers generally be made of PVC or ABS plastic. Though standard PVC/ABS sewer pipes come in diameters ranging from 1 1/2 to 4 inches, larger diameter pipes are available from specialist plumbing supply houses. Replacing a broken section of 5-inch sewer pipe requires cutting it out and replacing it with the same diameter PVC pipe, with flexible rubber couplings attached at both ends.
Mark the existing 5-inch diameter sewer pipe six inches on each side of the damaged area. Make a straight perpendicular cut through the pipe at both marks. For lead pipe use a hacksaw, for clay use a reciprocating saw and for cast iron use a snap cutter. Scrape off any burrs from the cut pipe ends using a utility knife.
Measure between the two cut pipe ends, and cut a section of 5-inch diameter PVC pipe to the same length --- use a handsaw or circular saw. Remove burrs. Mix some soapy water and brush it onto the outside end of both existing pipes. Push a 5-inch diameter flexible rubber coupling fully onto the end of each existing pipe.
Brush soapy water onto both outside ends of the new PVC pipe section; position the section between the existing pipe ends. Push the rubber couplings halfway onto each PVC pipe so that the couplings are half on the existing pipe, and half on the PVC pipe. Tighten the metal hose clamps surrounding the ends of each coupling using a screwdriver.
If 5-inch diameter PVC pipe is not available, use 4-inch diameter PVC pipe and attach it to the existing pipe with flexible rubber reducing couplings --- 5-inch diameter on one side and 4-inch diameter on the other. However, make sure that local building codes allow for this smaller diameter pipe to be installed. To use a snap cutter, place the cutter's chain around the pipe in the place where it needs to be cut. Hook the chain onto the small hook at the end of one of the handles. Quickly push the cutter's handles together to make a clean, straight cut through the cast iron pipe.
Wear a face mask and work gloves when cutting pipe.