Incorporating First Defense® High Capacity Technology

Capture and retain stormwater sediment, trash and floatables in a unit that saves site space and adapts to smaller or logistically difficult site locations. First Defense® is a versatile stormwater separator known to have the highest approved flow rates around the worldThis provides engineers with the confidence in specifying quality products and installation costs for the contractors. It also works with single and multiple inlet pipes and inlet grates. It is easily maintained from the surface by a standard vacuum truck. 

Designed with site flexibility in mind, the First Defense® stormwater separator provides versatile capture of gross pollutants (GP), total suspended solids (TSS) and floatables that allows engineering consultants and specifiers to maximize available site space without compromising stormwater treatment level.

The First Defense® works easily with single or multiple inlet pipes and inlet grates, and is independently tested, verified and approved throughout many countries around the world.

Targeted Pollutants

  • Gross pollutants (GP)
  • Litter – i.e. rubbish, paper, plastic, styrofoam, metal and glass
  • Debris – organic material including leaves, branches, seeds, twigs and grass clippings
  • Floatables
  • Total suspended solids (TSS) i.e. Sedimentation


The First Defense® reliably treats stormwater runoff from impermeable surfaces across a broad range of catchments.

First Defense® also operates successfully as part of a treatment train alongside other proprietary or natural drainage features, for example as treatment before infiltration.

  • As part of water sensitive urban designs (WSUD)
  • Stormwater treatment at the point of entry into the drainage line.
  • Sites constrained by space, topography or drainage profiles with limited slope and depth of cover.
  • Retrofit installations where stormwater treatment is placed on or tied into an existing storm drain system.
  • Pretreatment for filters, infiltration and storage.

First Defense® is a registered trademark of Hydro International.

Reduces footprint size and is cost effective

The STS CYCLONE First Defense® provides space-saving, easy-to-install surface water treatment in standard sized chambers/manholes. Custom fibreglass and concrete versions are also available upon request. 

Adapt to site limitations

Variable configurations are available for the STS CYCLONE™ making connections simple to a range of pipe sizes and pipe types, multiple inlet pipes and inlet grates.

Prevent washout

Unlike many other stormwater treatment products available in the market, the First Defense®captures and retains the pollutants.  The low-energy vortex separation of the First Defense® eliminates excessive agitation of captured pollutants ensuring that these pollutants are not washed out during subsequent large rainfall events. 

Save installation time

Each STS CYCLONE First Defense® unit is delivered to site pre-assembled and ready for installationThe comes in a purpose designed and manufactured fibreglass chamber with pre-assembled First Defense® technology ready for a light weight single lift. 

1. Contaminated stormwater runoff enters the inlet chute from a surface grate and/or inlet pipe. The inlet chute introduces flow into the chamber tangentially to create a low energy vortex flow regime that directs sediment into the sump.

2. Treated stormwater exits through a submerged outlet chute located opposite to the direction of the rotating flow. Enhanced vortex separation is provided by forcing the rotating flow within the vessel to follow the longest path possible rather than directly from inlet to outlet.

3. Higher flows bypass the treatment chamber to prevent turbulence and washout of captured pollutants. An integral bypass chute conveys infrequent peak flows directly to the outlet chute, eliminating the expense of external bypass control structures.

4. Floatables are diverted away from the bypass chute into the treatment chamber through the floatables draw-off port.

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    Stormwater Treatment Solutions
    is a division of All Purpose Pumps