Septic Tank Lid
Each compartment of a septic tank has an access port which is sealed with a lid. These can either be concrete, plastic, or fiberglass depending on what type of tank is installed.
On new construction, when septic tank lids are buried more than 12 inches below finished grade, risers or access tunnels are installed on top of the tank lids, and are extended up to a point that is less than 12 inches from the ground surface or to grade.
Most common septic tank lids are the square concrete lids which are approximately 21". Some of the lids for larger tanks have 24" lids which can be either square or round.
The riser needs to be completely sealed to the tank to prevent ground water from entering the riser cavity, which may cause a flooding of the tank and the whole system. If the riser lid is located at grade, it shall be locked to prevent entry.
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