DC-904000-1.2, Duracast 4000 Gallon Plastic Water Tank | 904000 Keep your water stored in a tank you can rely on with Duracast’s 4000 gallon plastic water tanks. These storage tanks are made of FDA-approved resin so that you can safely store potable water. Rust-resistant and seamless, these tanks are designed to prevent your water from leaking. The durability of these tanks means you can keep them outdoors. The resin is UV stabilized to extend the life of the tanks and slow down damage caused by the sun. To keep water clean and slow the growth of waterborne algae, store water in green or black tanks. The darker colored tanks are more effective at keeping the green spectrum light from penetrating the tanks. This is a 1.2 specific gravity tank.