They are essential when the water has turbidity problems (excluding sand) due to the presence of silt, earth, clay, etc. The clarity of the water is ensured by a 98% quartzite filter bed of silica that works, as in nature, as a catalyst for suspended substances. Having reached a specific clogging limit (approx. 8-10 m3), the quartzite is washed with counter-current water flow and is finally washed in equal current. Electronic programming automatically programs all washing operations on predetermined days and hours. Drinking water treatment equipment per Ministerial Decree 25/12 and Ministerial Decree 174/04.