Poly Guard Crystals prevents hard water scale and iron build-up in water systems, equipment and appliances by forming a protective coating on the surface areas with continual exposure to water. Poly Guard is typically administered through our patented refillable cartridge. This cartridge is compatible with most filter housings and will treat up to 30,000 gallons of water, lasting up to six months. Poly Guard sequesters up to 12 GPG (200) PPM Hardness and 1 GPG (17 PPM) Iron. One pound of crystals will treat 20,000 gallons of water. Pro Poly Guard is NSF Certified to meet NSF/ANSI Standard 60 for drinking water additives.