NAC445A.9658. Septic tanks: General requirements.

     1. A septic tank included as part of an on-site sewage disposal system must:

     (a) Be constructed of durable materials designed to withstand expected physical loads and corrosive forces.

     (b) Be verified watertight by a test during installation.

     (c) Be installed so that the tank is level.

     (d) Be designed to provide for the settling of solids, the accumulation of sludge and scum, and access for cleaning.

     (e) Meet the requirements of the Uniform Plumbing Code, ASTM International, or other recognized construction code or design manual for the construction of septic tanks, as referenced by the design engineer.

     (f) Conform to guidelines established by the Division.

     (g) Have a liquid depth of at least 36 inches. A liquid depth of more than 6 feet must not be considered in determining tank capacity.

     (h) Have at least 12.5 percent of the tank volume for scum storage, with a minimum airspace of 9 inches.

     (i) Except as otherwise provided in subsection 4, have two compartments. The capacity of the inlet compartment must not be less than two-thirds of the total capacity of the tank.

     2. Septic tank inlets and outlets must allow free venting of tank gases back through the drainage system.

     3. The top of the tee or baffle for both the vented inlet and vented outlet must extend at least 12 inches below the level of the liquid. The bottom of the tee or baffle for both the inlet and the outlet must extend at least 12 inches below the level of the liquid. The invert of the inlet pipe must be at least 2 inches above the invert of the outlet pipe.

     4. Septic tanks may be installed in a series of not more than two. Each tank in the series must be a single compartment tank, and the volume of the first tank must not be less than two-thirds of the total capacity of both tanks.

     5. Each compartment of the septic tank must have at least one manhole to provide access into the compartment. Each manhole must have a minimum diameter of 20 inches. If the inlet compartment is longer than 12 feet, an additional manhole must be provided over the baffle or partition wall. If the tank is longer than 30 feet, an additional manhole must be added for each 10 feet of length. Manholes must be designed to minimize odors and to prevent unauthorized entry.

     6. The top of the tank must be at least 6 inches below the finished grade. If the top of the tank is more than 18 inches below the finished grade, each manhole required pursuant to subsection 5 must be extended to within 18 inches of the finished grade.

     (Added to NAC by Environmental Comm’n by R194-07, eff. 8-26-2008)