Pressure distribution


Pressure distribution applies effluent uniformly over the entire absorption area such that each square foot of bottom area receives approximately the same amount per dose at a rate less than the saturated hydraulic conductivity of the soil. This process promotes soil treatment performance by maintaining vertical unsaturated flow at all times and also reduces the degree of clogging in finer textured soils. Pressure distribution closely approaches uniform distribution.

A pressure distribution system consists of a pretreatment component to separate the major solid materials from the liquid, a screening device to protect the pump and drainfield orifices from solids, and a means to deliver specified doses of effluent, under pressure, to the distribution system (Converse, 1974; Converse, et al., 1975; Otis, et al., 1978). The distribution system consists of small 1 to 2 inch diameter laterals with small discharge orifices. A pressure head is created within the laterals, usually by means of a pump or siphon.

Pressure distribution is applicable to any system, which uses soil as a treatment medium and may improve long term performance of those systems. It is required by WAC 246-272 for certain site and soil conditions. Pressure distribution is also a required component for mounds and sand filters


To view the complete Recommended Standards and Guidance for Performance, Application, Design, and Operation and Maintenance of the Pressure Distributuion System you may follow the following links:

Pressure Distribution (Effective Date: April 5, 1999)

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