Step 1: Stormwater enters the unit via the inlet pipe. The SDD can be designed for an on-line or an off-line installation.
Step 2: The flow splitter evenly distributes and directs the incoming flow towards the two vortex drop shafts. The centrifugal and gravitational forces generated by the vortex separate the sediments and oil from the water.
Step 3: The sediment settles to the bottom of the tank and collects in the sediment storage area.
Step 4: The lighter oil particles and floatables will rise and remain trapped beneath the lower baffle.
Step 5: The flow continues its way around the lower baffle and flow continues towards the outlet hatch.
Step 6: Treated water exits the unit through the outlet pipe.
In the case of very high stormwater flows :
Step 7: The excess water flow overs the top of the flow splitter and then towards the outlet pipe.