Contaminated stormwater runoff enters the inlet chute from a surface grate and/or inlet pipe (red arrow). The inlet chute introduces flow into the chamber tangentially to create a low energy vortex flow regime that directs sediment into the sump while oils, floating trash and debris rise to the surface.

Treated stormwater exits through a submerged outlet chute located opposite to the direction of the rotating flow (blue arrow). 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.

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