25 lb. bag. Diatomaceous Earth (D.E.) filtration, long recognized for supplying the highest clarity water, provides important health benefits to both commercial and residential pool owners and patrons by reducing exposure to water-borne pathogens. D.E. filter grids should be cleaned a minimum of once a season on outdoor pools or seasonal use pools and once every four to six months on indoor or continuous use pools and spas. Please monitor your flow rate and pressure to determine if your filter grids need to be cleaned more often. Add 1 lb. of D.E. per 10 sq. ft. of filter area.