Underground and Aboveground tanks are available in NSF-listed models with an NSF label affixed to it. An extensive level of testing and facility inspection is necessary to obtain approval to apply an NSF label to a tank. Most competitive products simply use listed materials and don''t subject their products to NSF''s rigorous tests. This can be verified on NSF''s website of listed products. An NSF-listed potable water tank is available in both underground and aboveground models.