Section 410IAC6-8.3-66. Distribution box specifications

   (a) Concrete distribution boxes shall be constructed of concrete with a compressive strength of four thousand (4,000) pounds per square inch or greater. Other materials may be considered on a case-by-case basis. All materials must:

(1) be resistant to corrosion and decay; and

(2) have sufficient structural strength to contain sewage and resist lateral compressive and bearing loads.

  (b) The minimum interior dimension of a distribution box shall be twelve (12) inches.

  (c) The distribution box shall be fitted with a watertight, removable lid for access. The distribution box may be fitted with a riser to the ground surface. The riser joints and the lid connection to the riser must be watertight.

  (d) The interior bottom of the distribution box shall be at least four (4) inches below the invert elevation of the effluent ports. A minimum of eight (8) inches freeboard above the invert elevation of the effluent port shall be provided.

  (e) The influent port shall be located or baffled to prevent unequal distribution of effluent to the distribution system. If baffles are provided, the baffles and their mounts or retainers shall:

(1) provide a passageway for effluent between the box bottom and the bottom edge of the baffle of not more than two (2) inches; and

(2) extend to one (1) inch above the top of the inlet.

  (f) An elbow or sanitary tee in the vertical position may be used in place of a baffle, as follows:

(1) If an elbow is used, the elbow must:

(A) be a ninety (90) degree elbow;

(B) be turned down into the distribution box with the end of the elbow not more than two (2) inches above the bottom of the distribution box; and

(C) include a weep hole in the upper part of the elbow.

(2) If a sanitary tee is used, the bottom of the sanitary tee must be not more than two (2) inches above the bottom of the distribution box and the top of the sanitary tee at least one (1) inch below the lid.

  (g) Each distribution box shall be designed to split the effluent flow equally among the effluent ports. All effluent ports shall be:

(1) at the same elevation;

(2) of the same diameter; and

(3) located at an elevation at least one (1) inch lower than the influent port.

(Indiana State Department of Health; 410 IAC 6-8.3-66; filed Oct 19, 2012, 2:06 p.m.: 20121114-IR-410120156FRA)