Pro Poly Guard Scale & Rust Preventer (Liquid) is specifically formulated to prevent hard water scale and iron staining in commercial, industrial and residential potable water applications. Poly Guard forms a protective coating on metal and plastic surfaces preventing scale, corrosion and copper leaching. Inject Poly Guard by chemical feed pump into the raw water system as close to the source as possible. This product is NSF Certified to meet NSF/ANSI Standard 60 for drinking water additives.