Drainage field

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Terms & Synonyms

Official WHO Definition

Area of land used for infiltration of wastewater into soil (WHO 1992).Part of a septic system for managing wastewater from small or low dense communities, the term refers to a field (leachfield) where the tank effluent is distributed; natural processes purify the liquid as it drains through the soil (EPA 1994) 

Other Definitions


Interpretations and Explanations

Drainage fields consist of gravel-filled underground trenches, called leachlines or drainage trenches, that allow the liquid effluent from a septic tank to infiltrate the ground. Open-jointed (stoneware) or perforated polyvinyl chloride (PVC) pipes lead the liquid effluent into the drainage field.Initially, infiltration may be fast, but after several years the soil clogs and an equilibrium infiltration rate is reached. If the sewage flow exceeds the equilibrium rate of the soil, sewage will eventually surface over the drainage field. Pressure can be taken off drainage fields by reducing the amount of water and solids flowing into the solids interceptor tank (e.g. by installing toilets that use less water – “low-flush” toilets), or by preventing sullage from entering the tank (WHO 1992).


EPA (1994)  Environmental Planning for Small Communities: A Guide for Local Decision-Makers. September 625/R-94/009WHO (1992) A guide to the development of on-site sanitation

WHO Lexicon page (translations and examples)

See also

External Resources


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