DC-900400-1.2, Duracast 400 Gallon Plastic Water Tank | 900400 When you have a large amount of water to store, take advantage of these bigger storage tanks. Duracast’s 400 gallon water tanks are still lightweight and require little maintenance. The molded-in measurement graduations allow you to keep track of content levels. The lids on top of each tank are large enough to fill and drain water without spilling. The green and black tanks will help retard the growth of waterborne algae. If keeping tanks indoors, consider a white-colored tank. The natural white tanks are translucent so that you can see their contents. Common uses for these plastic water tanks include collecting rainwater, irrigating and storing potable water.