Swmp

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        Retention Tank

        The Graf retention system is a combination of detention and rainwater harvesting. The system
        works much like the detention tank however in this case, the rainwater is harvested and used
        by the property owner for their own needs in addition to the authorities required detention
        volume of the site.

        For example, rainwater harvesting can be used for:
        • Watering gardens • Flushing toilets • Washing machines • Cleaning

        The use of rainwater means that up to 50% of drinking water                            available for temporary storage. Following the rainfall event, the
        can be saved, and up to 85% of water can be saved for                                  position of the outflow prevents the detention tank from being
        commercial properties.                                                                 completely emptied, while the usable volume remains in the tank.
        The retention tank is designed so that the rainwater first fills the
        retention (rain harvesting) capacity. When the capacity is full, the
        outflow is activated and the detention capacity also becomes

        Graf Minimax Filter



        Controlled flow outlet




        Connection to storm water

                                                                                                                                   Storm water detention

        Pump


                                                                                                                                   Rainwater harvesting




                                                Please note: Graf Minimax filter removes the requirement for a trash grate

                                                The volume distribution (detention volume/retention volume) can be individually manufactured
                                                according to your specifications.


        Retention Tank Outflow Rate


                  1
                              limited outflow

                                            2
                                                                       1. Outflow rate
                                                                          without controlled
                                                                          flow device

                                                                       2. Outflow rate
                                                                          with controlled
               Storage        Flow duration in hrs
               volume holds   Retention volume increases
                                                                          flow device




        8 GRAF UNDERGROUND STORM WATER TANKS