Downstream Defender®

The Downstream Defender® is an advanced hydrodynamic vortex separator, designed to create a low energy rotational flow to facilitate pollutant separation and capture. The Downstream Defender® provides efficient capture and retention of fine and coarse particles, hydrocarbons, oils and floatable debris from stormwater runoff.

The Downstream Defender® can accommodate a wide range of flows and other site-specific requirements due to its innovative design. It is the perfect choice for catchment areas likely to contain high quantities of pollutants.

Advantages include

  • Pre-assembled to facilitate ease of installation
  • Integral high-capacity bypass diverts large peak flows without the requirement for offline systems
  • Enhanced vortex separation generating a long flow path to ensure capture and retention of pollutants

Sizing for the Downstream Defender® is determined by design flow rates to meet a water quality treatable flow rate. Each device has a maximum treatable flow rate and a maximum peak flow rate.

Halgan supplies a variety of designs for the Downstream Defender®, catering for: variable depths to invert, required treatable flow rates, WSUD MUSIC Modelling requirements.

The unique flow-modifying internal components also minimize hydraulic losses. There are no internal weirs or orifices; large clear openings ensure low head loss at peak flow rates with little risk of blockages that cause upstream flooding.

The Downstream Defender® can be used to meet a wide range of stormwater treatment objectives. Selection and layout of the appropriate Downstream Defender® model depends on site hydraulics, site constraints and local regulations.


  • New developments, retrofits, utility yards, streets and roadways, car parks, industrial and commercial facilities, wetlands protection
  • Pretreatment for filters (Up-Flo Filter®), infiltration and storage
  • Water Sensitivity Urban Design Projects (WSUD)

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