Graf Carat S 1700 Gallon Extension Tank

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Product Overview

Graf Carat S 1700 Gallon Underground Extension Tank. This tank is intended to be used as a cost-effective extension tank to increase the storage capacity in conjunction with other Carat tanks which provide the access for pumps and filtration.

The Tank Guaranteed Not to Collapse When Empty*

  • 1700 Fully-usable gallons of additional storage

* When installed in compliance with manufacturer's installation instructions

Note: This is the Extension Tank which is intended to be used with the 1700 Gallon Carat S Underground Tank which can be found by clicking here.





Easy and safe assembly

  • The patented quick connection (illustrated in green), allows the Carat tank to be assembled without screws in only few minutes. Disassembly is possible at any time.
  • The first-class EPDM material used in the profile seals (illustrated in yellow), has been laboratory tested to last more than 25 years.
  • The centering bolt (illustrated in orange) assures the accurate and easy assembly of the two half shells preventing any leaks


More advantagesGraf Carat Extension Tank Dimensions

  • Variable burial depth: 30" to 70.9"
  • 70.9" maximum burial depth even in groundwater
  • Unique in the world! – a global innovation: unique manufacturing process produces the highest stability due to latest techniques
  • Unique fit accuracy of the components thanks to new production process
  • Consistent quality due to German TÜV safety testing and production monitoring
  • Groundwater stable up to the middle of the tank due to extremely rigid construction
  • Secure investment with market leading 15-year warranty
  • Made from high quality Duralene; easy to recycle
  • Can be expanded as required


  • The global innovation – the new tank generation of the Carat rainwater underground tanks have been specially developed for rainwater harvesting
  • Frost-proof installation underground
  • Groundwater stable up to the middle of the tank due to extremely rigid construction

Logistical advantages of the Carat:

The Carat tank consists of two half shells which can be stacked on top of each other, allowing multiple tanks to be stacked on a single pallet for shipping. For example, it is possible to stack five 1,700 gallon Carat tanks on a single pallet. This allows a standard 40 ft. shipping container to house a total tank volume of up to 34,000 gallons! The tanks' unique stacking feature directly reduces transport costs and environmental impact from vehicle emissions.




Graf Carat Tank Specifications

Download Graf Carat Tank Spec Sheet

Download Graf Carat Tank Installation and Maintenance Manual

Graf Carat Tank Assembly Video

View Video of Carat Tank Assembly