DC-901500-1.2, Duracast 1500 Gallon Plastic Water Tank | 901500 These plastic water tanks can be used for a variety of purposes including fire sprinkler systems, farming, municipal utilities, construction and rain harvesting. The polyethylene resin is FDA approved so you can also use these tanks to store an emergency supply of potable water. Rotationally molded, these tanks have a one-piece structure that reduces the chance for leaks. Green and black tanks are better at blocking out the green spectrum of sunlight, slowing the growth of waterborne algae. Natural white tanks are good for indoor use because they are translucent and allow you to easily view content levels. The gallon calibrations molded into each tank allow you to calculate when tanks are too low. This is a 1.2 specific gravity tank.