Filter rock definition
Filter rock means graded, rounded rock or gravel, or both, not subject to degradation by common pool chemical used to support filter media.
Filter rock means graded, rounded rock or gravel, or both, not subject to degradation by common pool chemical used to support filter media. "FILTER SAND" means a specially graded type of permanent filter media. "FILTER SEPTUM" means that part of the filter element in a diatomite type filter upon which a cake of diatomite or other nonpermanent filter aid may be deposited.
Filter rock means specially graded rock and gravel used to support filter sand. 21. “Filter sand” means a specially graded type of permanent filter media.