Hydrodynamic Separators

Jensen Deflective Separator

With no moving parts, the Jensen Deflective Separator (JDS) is uniquely able to screen trash and debris, including floatables and both neutrally and negatively buoyant materials, from stormwater runoff without blocking the screen. Built with durable precast concrete, the JDS also captures total suspended solids, oil, grease, and other total petroleum hydrocarbon pollutants. Captured pollutants are retained without scouring, even under high flow bypass conditions. Capable of treating flows from 0.7 to 72 cubic feet per second, the JDS is verified by the New Jersey Corporation for Advanced Technology, certified by the New Jersey Department of Environmental Protection and certified as a Full Capture System for Trash Treatment Control by the California State Water Resources Control Board.



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Jensen Deflective Separator Inline

How It Works

Jensen Deflective Separator hydrodynamic separator diagram

The JDS offers a unique non-blocking and non-mechanical screening process with no moving parts and no power requirements.

  1. Stormwater enters the JDS unit from one or more inlet pipes, a grated drop or curb inlet.
  2. Incoming water collects in the fore bay of the inlet trough.
  3. Waters enter the separation and screening cylinder through the volute entrance in the diversion weir wall.
  4. Water entering the separation cylinder forms a spinning vortex, capturing all floatables and swirl concentrating suspended solids to the center of the separation chamber.
  5. The vortex flow pattern produces a washing force across the screen face, preventing it from becoming blocked, while allowing stormwater to pass through the screen and flow beneath the oil baffle.
  6. Oils, greases and other Total Petroleum Hydrocarbons (TPHs) are trapped within the integral oil baffle attached beneath the inlet bay.
  7. Settled and swirl concentrated suspended solids are captured in the sump which is typically cleaned out by a vactor truck.
  8. Flows larger than the JDS unit’s design treatment flow bypass over the diversion weir. Bypass flows do not scour out previously captured pollutants.


  • 100% trash and debris removal
  • 50% TSS removal
  • Sediments
  • Oil, grease, and other TPH
  • Standalone treatment applications
  • Pretreatment applications
    • Detention and infiltration systems
    • Biofiltration systems
    • Media or membrane filtration systems

Delivering value at every stage of the project lifecycle


  • Leverage proven continuous deflective treatment process for full capture of 100% of trash and debris ≥5mm.
  • Treat large flow ranges from .7 to 83 CFS with inline and offline units.
  • Save with the most cost effective treatment method per cfs of stormwater as compared to other structural BMPs.


  • Meet full capture requirements with state certified treatment systems.
  • Bid an equivalent system directly from the manufacturer to save time and money.
  • Receive a complete package quote that includes all your precast sewer and storm drainage products.


  • Install using standard methods with a JDS unit configured inside a precast manhole set below grade.
  • Maintain your system easily and safely by opening the unit through multiple large accessways and removing trash and debris with a standard vacuum truck.