The drained sand filter Geokit provided with an LDPE or a PVC geomembrane is a kit that includes an anti-contamination geotextile, a filtration grid, an LDPE or a PVC geomembrane, a watertight cap flange and an adhesive flexible flange. It is a rigid tool that is less susceptible to stresses typically encountered during field installation in rough sites (wells, rocky grounds etc). A puncture resistant Geokit made of a puncture resistant geotextile is also available. A drained sand filter is mainly made layers of sand and gravels. The purification process occurs thanks to the sand and microorganisms lying around sand grains. Effluents are later returned to the natural environment.