Drain pipes, known as sewer pipes, run from each water fixture in the home---sinks, toilet, shower,bath---down into the main sewer line, which runs either into a septic tank or the city sewer system. The drain pipes are attached to the main sewer line by a connecting coupling. The pipes are usually made of either Acrylonitrile Butadiene Styrene (ABS)---hard black plastic---or white PVC plastic. Rerouting these pipes requires finding a suitable new place to connect the drain into the main sewer line and then plan a route from that point to the location of the water fixture.
Cut through the existing drain pipe 12 inches from where the connecting coupling is attached to the main sewer line, using a hacksaw. Remove burrs with a work knife. Apply ABS glue around the cut and the inside of an ABS end cap. Push the end cap onto the end of the cut pipe and hold for 30 seconds. Now remove the drain pipe that is no longer needed.
Mark the main sewer line at the point where the connecting coupling is to be installed. Make a second mark 2 inches away from the first. Cut through the pipe at both marks; the cuts will be parallel with each other. Remove any burrs.
Apply ABS glue around both cuts, as well as the inside of a connecting coupling. Squeeze the coupling between the two pipe cuts, making sure the coupling's side spout is on top, and hold in place for 30 seconds.
Glue the inside of the coupling's spout and on the end of a new piece of sewer pipe. Push the pipe into the spout and hold for 30 seconds. Install new pipe and couplings all the way to the water fixture. Use metal bracing and joist nails to secure the pipe and hold it in place.
All horizontal sewer pipe is installed at a gradient to allow for waste to travel down the pipe. Check with the local permit office for the correct gradient in your area. If using PVC sewer pipe, first prime the pipe joints with PVC primer before using PVC glue. A connecting coupling is the same diameter as the main sewer line, and its side spout is the diameter of the new sewer pipe. If there is room, use a power saw to cut through the main sewer pipe, as it will be easier to make the cut straight.