How to Build a Sewage Tank

Get the permit for your system. Each municipality has different requirements regarding the installation of a septic system and the size of tank needed for the building. You may be required to have the system designed by a licensed engineer and you may be required to have a percolation test performed on your land to determine the types of material on-site and how well they will work with the system.

Prepare the site for the sewage tank. Have a licensed contractor excavate the area where your sewage tank will be located, per the engineered plans regarding depth and size. Layer the bottom of the hole with approximately 6 inches of gravel, to provide a solid base for the tank.

Set the rebar and the molds for your tank. Lay out the mold, per your design specifications, for the floor of the sewage tank. Floor molds can often be as simple as constructing a rectangle of dimensional lumber to accommodate the needed thickness of the floor. Lay the rebar per local building code, often 12-inch spacing on center. Bend and tie rebar to form the sides of the tank. Insert the waste pipe into the front and rear sides of the tank, per the plans, tying into place to secure and have the rebar inspected, as required by your building permit.

Pour the floor and sides of the tank. Pour the floor of the sewage tank, using the chute from the concrete truck from your concrete supplier. Trowel the cement to make it reasonably level and let cure. Place the side wall forms, per the manufacturer's instructions, bracing as instructed, and pour the four sides of the tank using the chute from the concrete truck. Trowel to level the tops of the walls and let it cure.

Create the tank lid. Lay a bed of sand, at least 4 inches thick and larger than the tank lid dimensions, near the tank site. Place the forms, rebar and the manholes for the tank lid on the sand. Pour the concrete, trowel to level and insert the eye bolts into the uncured lid, near each corner. Let cure completely, remove forms and lift by threading chains through the eye bolts and set into place on top of tank.