8.7.3.4.Distribution Pipe

(1) Except for a shallow buried trench, the distribution pipe used in the construction of a leaching bed shall be
  (a) not less than 3 in. trade size for gravity flow systems,
  (b) installed with a uniform downward slope from the inlet with a drop of not less than 30 mm and not more than
      50 mm for each 10 m of distribution pipe for gravity flow systems, and
  (c) installed within a layer of stone conforming to Sentence (5).

     (2) Prior to backfilling, the stone layer required by Clause (1)(c) shall be protected in such a manner so as to prevent
         soil or leaching bed fill from entering the stone by completely covering it with
     (a) untreated building paper, or
     (b) a permeable geo-textile fabric.

     (3) Every pressurized distribution pipe shall be self-draining so as to prevent freezing of its contents.

     (4) Every pressurized distribution pipe shall,
     (a) be not less than 1 in. trade size, and
     (b) have orifices of at least 3 mm in diameter, spaced equally along the length of the pipe to provide even distribution of
         the effluent.

     (5)   The stone layer required by Clause (1)(c) shall
     (a)   be comprised of washed septic stone, free of fine material, with gradation conforming to Table 8.7.3.4.,
     (b)   be not less than 500 mm in width,
     (c)   extend not less than 150 mm below the distribution pipe, and
     (d)   extend not less than 50 mm above the distribution pipe.

     (6) This Article does not apply to a distribution pipe within a leaching chamber.

                                                           Table 8.7.3.4.
                                                    Gradation of Septic Stone
                                         Forming Part of Sentences 8.7.3.4.(5) and 8.7.8.2.(6)

                                         Particle Size                         Percent Passing
                                           53 mm                                    100
                                           19 mm                                    0-5
                                           75 µm                                    0-1

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.