The Graf Top Tank™ is a heavy-duty above ground rainwater collection tank constructed from 100% recyclable polypropylene with UV inhibitors. Tried and tested more than 20,000 times. The tank with the sensational price-performance ratio for aboveground installations in the garden or cellar. quick connection latches secure the two halves over a durable solid profile seal. The tank can be used alone and it can also be extended to thousands of gallons.