DC-900350-1.2, Duracast 350 Gallon Plastic Water Tank | 900350 When you’re short on water, use a plastic tank to help replenish your supply. These plastic water tanks are excellent containers for collecting and storing rainwater. They are also perfect for keeping fresh drinking water. The polyethylene resin has been approved by the FDA, which means these tanks won’t contaminate or affect the quality of water. If storing potable water outdoors, use a green or black tank. Because these tanks are darker, they are able to block out the green spectrum of sunlight, slowing the growth of waterborne algae. White tanks are translucent, and better for viewing content levels. These tanks are equipped with gallon indicators so you can determine exactly how low or full tanks are at any given time.