Lime OUT Heavy-Duty Rust, Lime & Calcium Stain Remover easily dissolves the toughest hard water and rust stains. An effective hard water stain and limescale remover, its thick, fast acting, concentrated formula is great for use on vertical surfaces as it clings longer for maximum cleaning power. An excellent option for cleaning hard water deposits, Lime OUT is septic safe and safe for a variety of both indoor and outdoor applications.