Large, versatile yet lightweight

With a diameter of 2.5 m and a volume of up to 120 cubic metres, the Carat XXL underground tank is the largest tank supplied by Graf. The supersized tank offers storage capacities previously only available with concrete and steel tank models. The tank's modular concept enables it to store and retain rainwater, function as a wastewater tank for local wastewater disposal, or store process water and fire extinguishing water. This, combined with the low weight, increases flexibility and reduces complexity in planning and installation.

The Carat XXL underground tank is available in 18 different sizes with volumes ranging from 16,000 L to 122,000 L. In spite of its large capacity, the Graf Carat XXL has all the advantages of a plastic tank: Its low weight compared with a concrete or steel tank reduces transport costs. Tanks of up to 76,000 l can be transported without the need for an abnormal load vehicle. The lifting straps needed to move the tank are part of the scope of supply.

The low weight also saves time and money during installation. There is no need to lay gravel for truck and crane access, as is often the case with concrete or steel tanks. The tank can be easily manipulated with a stationary crane or even an excavator, saving even more time and therefore more money.

The reservoir's ribbed construction makes it extremely stable. With an earth covering of just 1 m, the Carat XXL can be driven over by a vehicle weighing up to 40 t. The sturdy tank can also be installed in groundwater up to its midway point. As a mark of its high quality, Graf offers a 25-year warranty on the XXL tank.

The Carat XXL underground tank is installed below a courtyard or lawn. The Graf telescopic dome shafts are thus continuously height-adjustable and inclinable by 5 degrees. In the colour 'Lawn Green' and thanks to its level connection with the top edge of ground, the tank covering suitable for pedestrian loading, can be safely walked over, and does not present an obstacle to mowing.

The cast iron telescopic dome shaft can be installed in a paved or asphalt courtyard and can be safely driven over by vehicles of up to 3.5 t. The iron telescopic dome shaft for trucks allows conventional cast concrete covers to be used.

As an option, the tank can be fitted with an extra tank dome. The tank comes with contact surfaces up to DN 200 as standard. If required, connectors up to DN 300 can be factory-fitted on the tank dome and face end.

If the tank is to be used to hold rainwater, extra-large accessory components are also available from rainwater specialist Otto Graf. For example, roof areas of up to 6000 m² can be drained with the Graf Optimax XXL filter. The Optimax XXL provides an impressive water yield of up to 95% or more and is extremely low-maintenance thanks to the self-cleaning filter principle. The integrated cleaning unit cleans the filter screen with four adjustable flat jet nozzles and can be automatically controlled with a Graf rainwater control panel. To supply consumers such as toilets in large buildings, Graf offers the DPA-IRM dual pump system with feeder pump. Other components, such as a calmed inlet and an overflow siphon, are available in sizes up to DN 300.

The Carat XXL underground tank is also available as a retention tank with drain regulator for rainwater retention. As a retention tank Plus, it is dimensioned slightly larger to allow rainwater to be harvested in addition to the required retention volume. 

The universal large tank is now also available as a firefighting water tank, supplied prefitted with all the necessary firefighting water accessory parts in accordance with DIN 14230. This reduces installation time and makes assembly easier. The tank is also supplied with an iron telescopic dome shaft for mounting conventional cast concrete covers.