PolyDrain FirstFlush®

Stormwater Filtration for Urban Runoff

The "first flush effect" refers to the initial surface runoff during a rainstorm and the resulting surge of concentrated water pollution. Corresponding high sheet flows wash the pollutants through storm sewers to local surface waters. Our engineers created a Best Management Practice (BMP) to counter the negative effects of urban runoff.

Any storm runoff filtration system will collect debris, capture hydrocarbons, and should reduce pollutants. Our PolyDrain stormwater filtration solution also manages the significant overland flow during initial runoff events. We prioritize the stormwater first flush treatment event by allowing prolonged rainfall to bypass the treatment media. This bypass minimizes pulsing and prevents concentrated pollutants from the "first flush effect" from continuing on to downstream waterways.

FirstFlush® is the perfect sustainable drainage solution to meet this critical stormwater filtration challenge.

PolyDrain FirstFlush
Frame and Grate Included Inlet Cut-Out Guides Removable Basket Insert Replaceable Filter Module Outlet Connections

Frame and Grate Included

The frame comes preinstalled on all catch basin units from the factory and the removable cover makes the unit easy to inspect and clean.

Inlet Cut-Out Guides

Concrete cut-out guides are cast into the sidewalls for easy connection to PolyDrain® channels on all four sides of the basin.

Removable Basket Insert

The removable basket allows easy inspection and cleaning of the installed filter module.  And, built-in overflow relief ensures that the system functions even in the event that a rain event exceeds the expected peak flow capacity.

Replaceable Filter Module

Replaceable filter media units are inserted inside the removable basket.  A wide variety of filter modules are available to address different site-specific contaminants.

Outlet Connections

Convenient drilling guides for 6" (150mm) outlets on all four sides of the basin or other pipe sizes can be fitted to the catch basin as required.

Storm Runoff Filtration Systems

Our FirstFlush® precast stormwater channels & filters are ideal for space-restricted sites where retention ponds and other structures aren’t feasible. We designed this system to filter oil, grease, and other hydrocarbons during the “first flush,” or the initial surface runoff during a rainfall, which typically occurs in the first 15 minutes.  

The PolyDrain® series of products features convenient precast construction, and PolyDrain FirstFlush® is an efficient choice for sites under 100 acres where low-volume loads are expected.

Precast Storm Runoff Stormwater Filtration Systems



If you need a storm runoff filtration system that follows best management practice (BMP) and offers superior performance, FirstFlush® gets the job done. This system provides all-in-one functionality—handles sheet flow, controls vectors, collects debris, treats bacteria, and captures hydrocarbons all at once. The FirstFlush® precast stormwater channel systems can use any of the following filtration media and fabrics:

  • Standard Filtration “Blankets”
  • Antimicrobial Filtration Media
  • Hydrocarbon Media
  • HMR – Heavy Metals Removal Media
  • Mixed Media

The 2600FF series of filtration catch basins feature a two or three-part, stackable structure that is made of polymer concrete and comes with a grated cover.  It can be used in conjunction with the PolyDrain Trench Drain or as a stand-alone unit.  The basket inserts that hold the replaceable filter have built-in overflow relief.  Units are easy to inspect and clean.  Basket and filter modules can be retrofitted to existing PolyDrain 600 Series catch basins.

First Flush





Debri Volume

(cu. ft)

Bypass Flow Area


Details Sheet

(.dwg .pdf)

(Coming Soon)
20 x 13 x 32
FirstFlush Catch Basin Filter
20 x 13 x 48