TABLE OF CONTENTS A septic tank can be made of welded steel, monolithic concrete, fiberglass, or any other approved material. All septic tanks have to be watertight and constructed as an individual structure, and they must be designed and built to withstand anticipated loads. Precast tanks and tanks built on site must be authorized by the appropriate approval agency.
All septic tanks must have two compartments. Code requires the inlet compartment to be not less than two-thirds of the total capacity of the tank, and the capacity cannot be less than 500 gallons. This means that a minimum size for a modern septic tank is 750 gallons. The secondary compartment must not be less than 250 gallons. If a tank has a capacity of 1,500 gallons, the secondary compartment must not be less than 5 feet long.
The liquid depth of a tank must not be less than 30 inches and a maximum average of 6 feet is required. The total depth cannot be less than 8 inches greater than the liquid depth.
Cylindrical tanks must not be less than 48 inches in diameter. Rectangular tanks must be constructed so that the longest dimensions are parallel to the direction of flow.
Open-end coated sanitary tees or baffles made of approved materials constructed to distribute flow and retain scum in a tank or compartment are required on the inlet and outlet of all tanks. Inlets and outlets must be equipped to prevent a sewer from entering beyond the inside...
