To add a riser to a septic tank, pick the material you want to use for construction, dig down to the tank to gain access to the septic tank lid, fix an adapter ring, install the riser, and attach a new lid. A measuring tape, a shovel and pipes are necessary for the project.
The are three types of materials to choose from when constructing a riser, namely polvinyl chloride, polyethylene and concrete. Choose a type that suits your project. Decide whether to install the risers above or below the ground. To determine the number of risers needed, measure the distance between the tank and the place you intend to install the new septic tank lid. Risers come in 6- and 12-inch measurements.
Use a shovel to break up the earth around the tank to expose the lid. Dig at most 3 feet deep if you want to install the risers below the ground. Dig 2 feet around the lid to provide enough space for easy installation. Pry the lid off the tank.
Insert the adapter ring into the opening to the tank, and secure the ring with concrete. Place the risers above or below the ground, and fasten them together with screws. Purchase a new lid basing on the size of the risers, and fasten it to the top of the terminal riser with pins.