1000 Gallon Underground Water Storage TanksBEST Seller! IN STOCK NOW and Selling FAST A cistern is a simple and surefire way of bringing your water costs down. From their prime purpose, which is holding water and storing it for future uses, cisterns are also utilized in a number of applications from toilet flushes, irrigation to deviating water from buildings and streets. This is the Custom Roto Molding 1000 Gallon Cistern Burial Tank. Features: Capacity: 1000 Gallons 22" Gasket Locking Lid 2