The Ontario Building Code | Construction Requirements
8.7.8.2. Construction Requirements
(1) The treatment unit used in conjunction with a leaching bed constructedas a Type B dispersal bed shall provide an effluent quality that does not exceed the maximum concentrations set out opposite a Level IV treatment unitin columns 2 and 3 of Table 8.6.2.2.
(2) AType B dispersal bed shall be,
(a) rectangular in shape with the long dimension parallel to the site contours,
(b) not more than 1 000 mm in depth measured from the bottom of the stone layer to the finished grade when installed in soil with a percolation timethat exceeds 15 min, and
(c) backfilled with leaching bed fill so as to ensure that, after the leaching bed fill settles, the surface of the leaching bed will not form any depressions.
(3) The bottom of the stone layer shall be at least 600 mm above the high ground water table, rock or soilwith a percolation time greater than 50 min.
(4) The effluent shall be distributed over the Type B dispersal bed through a pressurized distribution system having a pressure head of not less than 600 mm when measured to the most distant point from the pump.
(5) The distribution pipes shall,
(a) be self-draining so as to prevent freezing of their contents, and
(b) have orifices of at least 3 mm in diameter, spaced equally along the length of the pipes.
(6) The stone layer containing the distribution pipes shall,
(a) be comprised of washed septic stone, free of fine material, with gradation conforming to Table 8.7.3.3.,
(b) extend not less than 250 mm below the distribution pipe, and
(c) extend not less than 50 mm above the distribution pipe.
(7) Thedistribution pipes shall be spaced not more than 1.2 m apart with the outermost pipe spaced not more than 600 mm from the edge of the bed.
(8) The pump chamber shall be sized to provide sufficient storage volume so that the effluent is evenly dosed on an hourly basis over a 24-hour period.
(9) When there is more than one Type B dispersal bed in a leaching bed, the Type B dispersal beds shall be separated by at least 5 m measured from the edge of the stone layers.
(10) A Type B dispersal bed shall not be located closer than the minimum horizontal distances set out in Table 8.2.1.6.B. and these distances shall be increased when required by Sentence 8.7.4.2.(11).