(A) Frost protection. Supply pipes must be protected from freezing where the pipe passes under driveways, sidewalks, roadways, or other areas where deep frost penetration is expected.
(Prior Code, Ch. 506 § 12.1)
(B) Gravity distribution.
(1) Serial distribution must be used to distribute effluent to individual trenches in a soil treatment system unless the necessary elevation differences between trenches for drop boxes cannot be achieved by natural topography or by varying the excavation depths, in which case parallel distribution shall be used. If drop boxes are used, they must meet the following standards:
(a) The drop box shall be watertight and constructed of durable materials not subject to corrosion or decay.
(b) The invert of the inlet pipe shall be at least 1 inch higher than the invert of the outlet pipe to the next drop box.
(c) The invert of the outlet pipe to the next trench shall be no greater than 2 inches higher than the crown of the outlet pipe of the trench in which the box is located.
(d) When sewage tank effluent is delivered to the drop box by a pump, the pump discharge shall be directed against a wall or side of the box on which there is no outlet.
(e) The drop box shall be covered by a minimum of 6 inches of soil and it shall be placed on firm and settled soil.
(f) An inspection pipe at least 4 inches in diameter must be provided and capped flush with or above finished grade.
(2) Systems using valve boxes shall comply with the following requirements:
(a) The valve boxes shall be watertight and constructed of durable materials not subject to corrosion or decay.
(b) The invert of the inlet pipe shall be at least 1 inch higher than the inverts of the outlet pipes to the trenches.
(c) When sewage tank effluent is pumped to a valve box, either a baffle wall must be installed in the valve box or the pump discharge must be directed against a wall or side of the box on which there is no outlet. The baffle must be secured to the box and extend at least 1 inch above the crown of the inlet pipe.
(d) The valve box shall be covered by a minimum of 6 inches of soil and it shall be placed on firm and settled soil.
(e) An inspection pipe at least 4 inches in diameter must be provided and capped flush with or above the finished grade.
(3) Distribution boxes must meet the following standards:
(a) The box must be watertight and must be constructed of durable materials not subject to corrosion or decay.
(b) The distribution box shall be covered by a minimum of 6 inches of soils and it shall be placed on firm and settled soil. An inspection pipe must be provided and capped flush with or above the finished grade.
(c) The inverts of all outlets must be set and maintained at the same elevation.
(d) The inlet invert must be either at least 1 inch above the outlet inverts or be sloped such that an equivalent elevation above the outlet invert is obtained within the last 8 feet of the inlet pipe.
(e) Each drainfield trench line must be connected separately to the distribution box and must not be subdivided. Distribution boxes must be connected to one another if each box has distribution pipes.
(f) When sewage tank effluent is delivered by pump, either a baffle wall must be installed in the distribution box or the pump discharge must be directed against a wall or side of the box on which there is no outlet. The baffle must be secured to the box and must extend at least 1 inch above the crown of the inlet pipe.
(4) (a) Distribution pipes used in trenches or beds for gravity distribution must be at least 4 inches in diameter and must be constructed of sound and durable material not subject to corrosion or decay or to loss of strength under continuously wet conditions. Distribution pipes must have a load bearing capacity of not less than 1,000 pounds per lineal foot.
(b) Distribution pipes used for gravity distribution must have 1 or more rows of holes of no less than 1/2 inch in diameter spaced no more than 40 inches apart. Holes must be spaced to prevent failure due to loads.
(c) The distribution pipe for gravity distribution must be laid level or on a uniform slope away from the distribution device of no more than 4 inches per 100 feet.
(d) Gravity distribution pipes in seepage beds must be uniformly spaced no more than 5 feet apart and not more than 30 inches from the side walls of the seepage bed.
(Prior Code, Ch. 506 § 12.2)
(C) Pressure distribution.
(1) Pressure distribution must be used for the following soil treatment systems:
(a) All mound systems;
(b) All at-grade systems; and
(c) Systems where the soil percolation rate is 0.1 to 5 minutes per inch if the effluent is pumped to a seepage bed or to trenches that are all at the same elevation.
(2) Distribution pipes used for pressure distribution must be constructed of sound and durable material not subject to corrosion or decay or to loss of strength under continuously wet conditions.
(3) All pipes and associated fittings used for pressure distribution must be properly joined together. The pipe and connections must be able to withstand a pressure of at least 40 pounds per square inch.
(4) Perforations must be no smaller than 3/16-inch diameter and no larger than 1/4-inch diameter. The number of perforations, perforation spacing and pipe size for pressure distribution laterals must be as shown in Table IV. The friction loss in any individual perforated lateral must not exceed 20% of the average head pressure on the perforations.
Maximum Allowable Number of 1/4-Inch Diameter, or Smaller Perforations per Lateral
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Perforation Spacing in Feet
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Pipe Diameter - Normal and Inside
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(5) Perforation holes must be drilled straight into the pipe and not at an angle. The perforated pipe laterals must be installed level with the perforations downward. Perforation holes must be free of burrs.
(6) Laterals must be spaced no further than 60 inches apart in seepage beds and mound rock beds and must be spaced no further than a horizontal distance of 30 inches from the outside edge of a drainfield rock layer.
(7) Laterals must be connected to a header or manifold pipe that is of a diameter such that the friction loss in the header or manifold will be no greater than 5% of the average head at the perforations. The header or manifold pipe must be connected to the supply pipe from the pump.
(8) Perforated laterals must be designed and installed in such a way that no perforations are located closer than 12 inches from the edge of the drainfield rock.
(Prior Code, Ch. 506 § 12.3)