Swmp

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        Detention Tank

        Storm water detention systems play an important role in the reduction of storm water flow during
        rainfall events and help reduce strain on the public storm water network, particularly in built up areas.
        Detention systems usually consist of a tank volume which is                                     emergency overflow will operate if the tank ever exceeds its
        used for the temporary storage of storm water in the event of                                   maximum level. The detention tank water discharges slowly into
        heavy rainfall, and a controlled flow device to limit the incidence                             the storm water network until it is completely empty and remains
        of localised flooding by controlling the rate of water flow into                                available once more as a temporary storage tank for the next
        the storm water system. A trash grate is highly recommended                                     rainfall event.
        to avoid blockage of the controlled flow outlet. Please note the




        Inlet water pipe


        Telescopic shaft and lockable manhole


        Emergency storm water overflow




        Controlled flow outlet



        Connection to storm water



        Inlet calming pipe




                                                                      Please note: Trash grate may be required with detention tank (refer p10)




        Detention Tank Outflow Rate

                                           1
                                                    limited outflow
              flow rate in l/sec.




                                                   2
                                                                                1. Outflow rate
                                                                                   without controlled
                                                                                   flow device

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




        6 GRAF UNDERGROUND STORM WATER TANKS