Low-pressure drainfields are an excellent treatment option in many onsite applications. A key advantage of low-pressure systems is even distribution of pretreated effluent over the media surface. Whether a media-filled trench, chamber system, shallow narrow drainfield or other type of soil absorption system, low-pressure application of pretreated septic tank effluent promotes even biomat development and helps ensure good final treatment and dispersal into the natural soil treatment environment. In addition, the upward spray of effluent through a network of orifices into orifice shields provides “impact flow,” wherein oxygen transfer is promoted, enhancing the aerobic treatment capabilities of the soil. Designers
