Low Pressure Pipe Systems (See endnote 29)
This is a soil absorption system, leading from a septic tank or aerobic unit, of a shallow, pressure-dosed series of small-diameter perforated pipes placed in narrow trenches. The pressure which comes from a pumping tank causes uniform distribution of the effluent in the system. The advantages of this system are that: the shallow placement in the trenches helps promote transpiration and furthers the growth of aerobic bacteria; absorption fields may be placed on sloping ground: there is improved distribution of the effluent because of the pressure unit; the periodic dosing and resting periods encourage aerobic conditions in the soil; and less land is needed for the absorption system. The disadvantages of the system include: the potential for clogging of the holes in the laterals by either solids or the roots of trees and bushes; the lack of storage capacity around the laterals; wastewater may accumulate in the trenches and saturate the soil; and a substantial need for continued maintenance of the system. Large systems have problems with hydraulic overloading because of infiltration of water, poor hydraulic design, improper installation, and orifice and lateral clogging.