By the time a sewer line exits a residence or the run to the main sewer line or septic system, the sewer line will be a 10 cm (4 inch) pipe. Today, outside sewer lines are almost entirely made of polyvinyl chloride (PVC) pipe. This type of sewer line makes laying and connecting the segments much easier than it was with the clay and cast iron lines of the past. Installing a new outdoor sewer line can be done quickly and efficiently once the trench is opened and the materials to do the job are on hand.
Dig a trench between the place where the sewer line exits the house and the main sewer line or septic tank. It is easiest to use a backhoe to accomplish this task although it can be done by hand if the ground is soft enough. If the trench is more than 90 cm or 1.2 m (3 or 4 feet) deep, use materials to shore up the sides to prevent being trapped in the event of a cave in.
Use wooden panels against each side with bracing between them to make working in a deep ditch safe. You can work between the panels for each piece of sewer line and move the panels along as you progress. Most sewer installations by amateurs are shallow enough that shoring is not necessary.
Place a rubber boot over the end of the sewer line as it exits the house. This rubber boot will act as a reducer to allow the 10 cm (4 inch) outside sewer line to be fastened to the smaller inside sewer line. Slide a clamp over the boot and use a screwdriver to tighten the screw on the clamp to secure it to the end of the inside sewer line.
Slide the larger clamp over the end of the boot. Push the first piece of 10 cm (4 inch) outside sewer line into the boot. Tighten the clamp to make a firm connection between the inside and outside sewer lines. Use a piece of wood or a rock to prop up the sewer line to get the proper amount of incline. Lay a level that is 1.2 cm (4 feet) long on top of the sewer line. The sewer line should slope so that the bubble in the level is about one-half of the bubble off of level sloping away from the building.
Shovel sand into the trench under the sewer line to hold it in the proper position. Remove the wood or rock prop once enough sand is in place to maintain the grade. Enough sand needs to be in the trench to completely surround the sewer line and cover the top of it slightly. Leave the last foot of the pipe uncovered so that the next connection can be made.
Make sure that the line is still in the proper position. Back fill the trench about three-fourths of the length of the piece of pipe to hold it firmly in place. Sewer line is made so that it tapers at the end. This allows you to put the next piece onto the previous piece without using a coupling.
Slide the next piece of sewer line onto the end of the previous piece. Follow the same process for installing this piece as the first piece. Continue this process until the sewer line reaches the main sewer or septic tank.
Install a rubber boot to make the final connection to the main sewer line or to the septic tank. This boot may function as a simple coupling or as a reducer depending on whether or not the connection is a 10 cm (4 inch) opening. Once the clamps are tightened to make this final attachment, finish the back filling to complete the installation.
Never climb into a deep trench without shoring the walls to prevent a cave in.