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25 Pa. Code § 73.42. Gravity distribution.

§ 73.42. Gravity distribution.

 (a)  Gravity distribution may be used in all instances, except where prohibited by §  73.43 (relating to pressurized distribution).

 (b)  The distribution system shall be arranged to provide for uniform distribution of the effluent.

 (c)  The flow shall be equally divided between individual laterals of a trench system or between seepage beds by use of a distribution box.

 (d)  The flow shall be divided between individual laterals in a seepage bed by a distribution box or by an unperforated pipe header connecting all laterals within the bed. Where distribution is via an unperforated pipe header, the terminal ends of all individual laterals shall also be connected with unperforated pipe.

 (e)  Distribution boxes shall comply with the following:

   (1)  When a distribution box is used, it shall be installed level to provide equal distribution of treatment tank effluent to each line. For testing purposes, the person responsible for the installation shall provide an adequate amount of water to check the level of the inlet and outlet lines.

   (2)  Construction shall comply with the following:

     (i)   Distribution boxes shall have removable covers.

     (ii)   Each lateral shall be connected separately to the distribution box.

     (iii)   The bottom of all outlets shall be at the same elevation, and the bottom of the inlet shall be at least 1 inch above the bottom of the outlet. The bottom of the outlet shall be at least 4 inches above the bottom of the distribution box.

     (iv)   Baffles shall comply with the following:

       (A)   A baffle shall be installed in the distribution box in the event that treatment tank effluent is discharged to the distribution box by a pump or siphon.

       (B)   The baffle shall be perpendicular to the inlet, be secured to the bottom of the box and extend vertically to a point level with the crown of the inlet pipe.

     (v)   A tee or elbow directed toward the bottom of the distribution box may be substituted for the baffle required by subparagraph (iv).

   (3)  Distribution boxes shall be installed on an adequate base of undisturbed or properly compacted earth or aggregate outside of the absorption area. Lightweight nonconcrete distribution boxes shall be anchored or otherwise secured to prevent shifting after installation. Adjustable distribution box weirs may be used on the outlet of the box.

 (f)  Laterals shall be a minimum of 3 inches in diameter unless a larger diameter is specified by local plumbing or building codes. Bends used in the disposal field shall be made with standard fittings.

 (g)  The maximum length of individual laterals employing gravity distribution is 100 feet.


   The provisions of this §  73.42 amended under section 9 of the Pennsylvania Sewage Facilities Act (35 P. S. §  750.9); The Clean Streams Law (35 P. S. § §  691.1—691.1001); and section 1920-A of The Administrative Code of 1929 (71 P. S. §  510-20).


   The provisions of this §  73.42 adopted August 2, 1971, effective August 14, 1971, 1 Pa.B. 1649; amended August 30, 1974, effective September 16, 1974, 4 Pa.B. 1805; amended January 21, 1983, effective January 22, 1983, 13 Pa.B. 508; amended November 7, 1997, effective November 8, 1997, 27 Pa.B. 5877. Immediately preceding text appears at serial pages (217325) to (217326).

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