Designed with site flexibility in mind, the First Defense stormwater separator provides versatile capture of sediments, trash and floatables that allows engineers to maximize available site space without compromising stormwater treatment level.

First Defense is available in different configurations to comply with stormwater regulations defined by various jurisdictions. 

Targeted Pollutants 

Approvals, Verifications and Certifications


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

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

  • As part of LID or LEED systems and Sustainable Drainage Systems (SuDS)
  • 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

Designed for

Coarse particles
High flow
Oils & hydrocarbons
Trash & floatables



Cut footprint size, cut costs

The First Defense® provides space-saving, easy-to-install surface water treatment in standard sized chambers/manholes.

Adapt to site limitations

Variable configurations will help you effectively slip First Defense® into a tight spot. It also works well with large pipes, multiple inlet pipes and inlet grates.

Prevent washout

The First Defense® retains the pollutants it captures. 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 rainfall events.

Save installation time

Every First Defense® unit is delivered to site pre-assembled and ready for installation, so installation is as easy as fitting any chamber/manhole.

How it works

How it works

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.

Technical information

Technical information

First Defense Sizing & Specifications

Case Studies

Case Studies