Underground water storage tanks are used for underground storage of potable drinking water, wastewater, & rainwater collection. So whether you call it a water tank or water cistern, as long as you are storing water underground these are the storage tanks for you. The ribbed design of water cistern tanks makes it capable of being buried underground, supporting the surrounding soil. Driving over or placing a sidewalk over a buried water cistern tank is not permitted and will void the warranty. Plastic underground water tanks (cistern water tanks) is a great alternative to concrete cisterns.