1. (a) General.

   1. (1) Septic tanks shall be of watertight construction.

   2. (2) Approved materials include:

      1. (A) Concrete;
      2. (B) Fiberglass; and
      3. (C) Polyethylene.
   3. (3) Approval of other materials will be considered on a case-by-case basis.

   4. (4) Septic tanks sold or installed in the State of Arkansas shall:

      1. (A) Meet the specifications in this part; and
      2. (B) Be approved by the Department of Health.
   5. (5) With the exception of wall and bottom thickness, pre-cast tanks and cast-in-place tanks shall meet the same design requirements.
2. (b) Cast-in-place concrete tanks. Permit applications utilizing a cast-in-place concrete tank shall include a plan approved by a professional engineer.

3. (c) Pre-cast concrete septic tanks.

   1. (1) Pre-cast septic tanks sold or installed in Arkansas shall be manufactured in accordance with the American Society for Testing and Material (ASTM) standard specification for pre-cast concrete septic tanks C 1227-05-cast septic tanks shall be constructed with high-strength concrete made with Portland cement and achieve a compressive strength of four thousand pounds per square inch (4,000 psi) at twenty-eight (28) days of age.
   2. (2) No aggregate used in the concrete mix is to exceed a diameter or length of one-half inch (1/2”).
   3. (3) Lightweight aggregates shall meet ASTM specification C 330 specification for lightweight aggregates for structural concrete.
   4. (4) Water used in mixing concrete shall be clean and free of injurious amounts of oil, alkalines, acids, salts, or other substances that may be incompatible with concrete.
   5. (5) Tanks shall be designed so they will not collapse or rupture when subjected to anticipated earth and hydrostatic pressures when the tanks are either full or empty.

   6. (6)

      1. (A) Pre-cast concrete tanks shall be reinforced with a minimum of #10, six inches by six inches (6” x 6”), welded concrete reinforcement wire overlapped a minimum of six inches (6”) and tied at the edges.
      2. (B) Reinforcement rods are required to be added at lift points.
      3. (C) Chairs, bolsters, braces, and spacers in contact with the forms shall have a corrosion-resistant surface.
      4. (D) Reinforcement shall:

4. (i) Be placed as near the center of the walls as possible; and

   1. (ii) Have a minimum of one inch (1”) concrete cover.
   2. (7) The department shall approve new forms or modifications to existing forms.

   3. (8)

      1. (A) The forms used in septic tank manufacture shall be sufficiently rigid and accurate to maintain the dimensions of the tank.
      2. (B) Casting surfaces shall be of a smooth, non-porous material.
      3. (C) Form releasing agents used shall not be injurious to the concrete.

   4. (9)

      1. (A) Concrete for the tank walls and floor shall be placed in the forms in a single, continuous pour.
      2. (B) The concrete shall be placed in the forms at a rate that allows the concrete to consolidate in all parts of the form and around all reinforcement steel and imbedded fixtures without segregation of materials.

      3. (C) The finished tank wall shall:

         1. (i) Be smooth; and
         2. (ii) Have a uniform thickness of not less than three inches (3”).

      4. (D) The lid and floor of the tank shall be:

         1. (i) Not less than four inches (4”) thick; and
         2. (ii) Adequately reinforced to support the load to which it may be subjected.

      5. (E) At a minimum, the lid shall be reinforced with:

         1. (i) #10, six inches by six inches (6” x 6”), welded wire mesh; and
         2. (ii) One-half inch (1/2”) reinforcement rods (which is #4 rebar) on eighteen-inch centers.
      6. (F) During delivery, the tanks are to be properly handled to ensure the installation of a tank that is watertight and otherwise in good condition.
   5. (10) Concrete septic, holding, and dosing tanks buried two feet (2’) or more shall require the manufacturer’s certification relating to structural integrity.

   6. (11)

      1. (A) Joints between the tank body and lid or between sections of multipiece tanks shall be sealed to prevent leakage during settling or shifting.
      2. (B) The sealant shall be resistant to corrosion and anaerobic activity and meet ASTM C990-09 Standard Specification for Joints for Concrete Pipe, Manholes, and Precast Box Sections Using Preformed Flexible Joint Sealants.
      3. (C) The inside joint seam gap, between the two (2) sections placed together before sealing, is not to exceed one-quarter inch (1/4”).
   7. (12) The lid and upper and lower sections of septic tanks shall be connected with noncorrosive mechanical devices by the manufacturer to ensure no separation occurs.

   8. (13)

      1. (A) Septic tank manufacturers are required to demonstrate the watertightness on their products when requested by the system designer, installer, or the authorized agent.
      2. (B) Vacuum testing shall be the only method for watertightness during septic tank manufacturers’ annual production plant inspection.
      3. (C) Testing for leakage may be done using either vacuum testing or water pressure testing at the time of delivery.
      4. (D) Small leaks found during testing may be sealed with an appropriate sealer.
      5. (E) In no case will a tank be considered acceptable which has evidence of large cracks or repairs that compromise the structural integrity and watertightness of the tank.

      6. (F) Vacuum testing.

         1. (i) Seal the empty tank and apply a vacuum to four inches (4”), or one hundred millimeters (100 mm) of mercury.
         2. (ii) The tank is approved if ninety percent (90%) of the vacuum is held for two (2) minutes.
         3. (iii) Manufacturers shall be capable of vacuum testing all tanks.

      7. (G) Water-pressure testing.

         1. (i) Seal the tank.
         2. (ii) Fill with water to the level of the top of the access port and let stand for twenty-four (24) hours.
         3. (iii) Refill tank.
         4. (iv) The tank shall be considered watertight if the water level is held for sixty (60) minutes.

   9. (14) Precast concrete septic tanks manufactured and installed in Arkansas shall be clearly, permanently, and legibly labeled with the following:

      1. (A) The name of the individual or company that manufactured the tank;
      2. (B) The liquid capacity of the tank in gallons;

      3. (C)

         1. (i) The inlet and outlet shall be indicated.
         2. (ii) Tanks with more than one (1) outlet shall utilize authorized tank penetration seals; and

      4. (D) The date of manufacture of the tank and lid.

         1. (d) Tank proportions.

   10. (1) The liquid depth of any tank compartment shall not:

       1. (A) Be less than thirty-six inches (36”); and
       2. (B) Exceed seventy-two inches (72”).
   11. (2) The minimum horizontal distance from the inlet to the outlet of any tank may not be less than seventy-two inches (72”).
   12. (3) Storage capacity is required above the liquid line to provide for that portion of scum that floats above the liquid in all septic tanks.
   13. (4) One (1) inch shall be provided at the top of the tank to permit the free passage of gas back to the inlet and house vent pipe.
   14. (5) For tanks having vertical sides, the distance between the inside top of the tank and the liquid level shall be twelve and five-tenths percent (12.5%) of the liquid capacity or nine inches (9”), whichever is greater.
   15. (6) In horizontal, cylindrical tanks, this distance should be equal to twenty percent (20%) of the tank diameter.

5. (e) Inlet and outlet.

   1. (1) Four-inch or larger sanitary tees shall be used as inlet and outlet devices in all septic tanks.
   2. (2) The septic tank manufacturer shall provide properly constructed inlet and outlet devices with each tank.
   3. (3) The effluent line leaving the tank shall be Schedule 40 PVC.

   4. (4)

      1. (A) The inlet invert shall enter the tank two (2) to four (4) inches above the liquid level in the tank to allow for a momentary rise in liquid level during discharges to the tank.
      2. (B) This free drop prevents black water and standing of solid material in the house sewer leading to the tank.

   5. (5) The inlet tee shall extend:

      1. (A) At least six inches (6”) below the liquid level in the tank; and
      2. (B) Above the liquid level to a minimum of one inch (1”) from the top of the tank.
   6. (6) In no case shall the inlet device be greater in length than the outlet device.
   7. (7) Outlet tees shall extend to a distance below the surface thirty-five percent (35%) to forty-five percent (45%) of the liquid depth.

6. (f)

   1. (1) Authorized outlet filter products are recommended on all septic tanks.

   2. (2) Outlet filters:

      1. (A) Have been shown to reduce total suspended solids (TSS) and biochemical oxygen demand (BOD); and
      2. (B) Should be utilized to protect and lengthen the life of the absorption area.
   3. (3) Proprietary gas deflectors designed to deflect or otherwise prevent solids from entering the outlet tee are not required but are recommended to increase the efficiency of the septic tank.
   4. (4) Where gas deflectors, outlet filters, or other devices requiring routine maintenance are installed in the tank, a service riser extending to grade shall be installed over the outlet inspection port.
   5. (5) Inlet and outlet baffles and devices shall be evaluated and authorized by the department prior to use.
   6. (6) Manufacturers may submit product samples and ancillary documentation to the department for evaluation.

   7. (7)

      1. (A) After evaluation, the department may give authorization for use in the state.
      2. (B) The list of authorized products will be routinely updated on the department website.

7. (g) Fiberglass and plastic septic tanks.

   1. (1) Fiberglass and plastic septic tanks shall comply with International Association of Plumbing and Mechanical Officials.
   2. (2) The manufacturer shall supply without charge satisfactory evidence of approval and compliance with IAPMO PS 1-2004e1 construction and manufacturing requirements.
   3. (3) Fiberglass and plastic septic tanks shall be tested for watertightness using one (1) of the prescribed methods found in IAPMO PS 1-2004e1.

8. (h) Service risers.

   1. (1) Access shall be provided:

      1. (A) Over the inlet and outlet tees or other devices; and
      2. (B) To each tank compartment by means of a service riser.
   2. (2) Maintenance ports shall be sealed and watertight.
   3. (3) Where the top of the tank is located below the finished grade, service risers shall extend to or above the finished grade.
   4. (4) The extension can be made using risers of authorized material and fitted with tight covers and secured to prevent unauthorized access.
   5. (5) Proper attention shall be given to the accident hazard involved when maintenance ports are extended close to the ground surface.
   6. (6) Service risers shall be a minimum of twelve inches (12”) in diameter.
   7. (7) Service risers providing access to a pump compartment or dosing tank shall be a minimum of eighteen inches (18”) in diameter.
   8. (8) Risers shall be installed by the manufacturer.
   9. (9) An entry prevention device is recommended for riser openings more than twelve inches (12’) in diameter.

Codification Notes: “IAPMO” means International Association of Plumbing and Mechanical Officials. "PVC" means polyvinyl chloride.