Curb inlet protection is sediment control designed for the curb and gutter openings found along streets and parking areas. Because a curb inlet takes in runoff sideways through a curb-face opening (rather than down through a flat grate), it needs a device built for that geometry: a curb inlet filter or barrier that filters gutter flow while letting water pass into the drain.

What is curb inlet protection?

Curb inlet protection (and the related curb inlet filter) addresses inlets that open at the curb line. Gutter flow runs along the curb and enters through the curb-face opening, sometimes with a grate alongside. Curb devices are shaped to sit in the gutter and across the opening so they filter the sediment-laden flow without fully blocking it, which would cause street flooding.

Curb inlet devices

• Curb bags and barrier bags that sit across the curb opening to filter gutter flow.
• Curb sacks with an open-top design for higher-capacity curb filtration.
• Curb units for grateless inlets that protect curb and median inlets without a grate.

Curb device comparison

All three are made in the USA and reusable. The grateless curb unit is the right answer when there is no grate to support a bag, which is common on median and some street inlets.

Inlet protection sizing guide

Devices are sized to the inlet opening. Measure the grate or curb opening first, then choose the device size that matches or just exceeds it. Common stocked sizes include:

Custom sizes are available for nonstandard openings. When in doubt, size up so the device fully addresses the opening without gaps where sediment could bypass.

Installation and maintenance

Correct installation and routine maintenance are what keep an inlet protection curb device working through a project. Most Dandy devices install without rebar, which makes setup fast and removal clean.

Installation steps

1. Identify the inlet and measure the opening. Confirm the inlet type (drop grate, curb, or field grate) and measure so the device matches the opening.
2. Position the device. For drop grates, set the sack or guard so the grate holds it in place. For curb inlets, position the bag or unit across the curb opening along the gutter line.
3. Seat and secure. Make sure the device fully addresses the opening with no gaps where flow could bypass. No rebar is needed for most models.
4. Verify overflow. Confirm built-in overflow features are clear so water can bypass safely in heavy rain rather than backing up.

Inspection and cleanout

• Inspect after every significant rain and on a regular schedule during active work.
• Remove accumulated sediment before it reduces capacity, typically when it reaches roughly one-third to one-half of the device, so filtration stays effective.
• Check for damage or displacement and reseat or repair as needed.
• Empty and reuse. Most devices are reusable; clean out the captured sediment and reinstall rather than discarding.

Document inspections and cleanouts. On regulated sites, that record is part of demonstrating compliance.

Inlet protection and stormwater compliance

Inlet protection is not just good practice, it is usually required. Under the federal Clean Water Act, construction sites that disturb soil are regulated through the National Pollutant Discharge Elimination System (NPDES) stormwater program, administered by the EPA and by state agencies. These permits require sites to control sediment so it does not leave the site through the storm system.

Where inlet protection fits in a SWPPP

Most regulated construction sites must prepare and follow a Stormwater Pollution Prevention Plan (SWPPP). The SWPPP lists the best management practices (BMPs) the site will use to control erosion and sediment, and inlet protection is a standard sediment-control BMP in that plan. Storm drain inlets on or near the site are protected so sediment is captured before it enters the public storm system.

Why compliance matters

• Avoiding fines: sediment discharges and unprotected inlets are common sources of stormwater violations and penalties.
• Protecting receiving waters: storm drains usually discharge untreated to creeks, rivers, and lakes, so sediment caught at the inlet never reaches them.
• Demonstrating good faith: properly installed and maintained, documented BMPs show inspectors the site is managing stormwater responsibly.

Always follow the specific requirements in your permit and SWPPP, since thresholds and accepted practices vary by state and locality.

Common curb inlet scenarios

Curb inlets show up in a few recurring situations, and the right device differs for each:

• Active street construction: a reusable curb bag across the opening filters gutter flow while traffic continues. It is quick to install and remove without rebar.
• Grateless median or curb inlet: with no grate to hold a bag, a dedicated grateless curb unit is the correct device, shaped to seal the open curb face.
• High-volume gutter flow: an open-top curb sack offers more capacity where runoff is heavy, reducing how often crews clean it out.
• Long curb openings: curb units come in lengths up to 12 feet, so a single device can span a wide municipal inlet rather than piecing smaller ones together.

In every case, the goal is the same: filter the sediment while keeping the gutter flowing, so the street does not flood and the storm sewer stays clear.

Why curb inlets need their own solution

A drop inlet sack made for a flat grate will not seal a curb-face opening, so curb inlets need devices designed for the gutter line. Using the right curb inlet protection prevents bypass (sediment slipping past an ill-fitting device) and avoids backing water up into the street. Matching the device length to the curb opening is the single most important sizing decision. The Inlet Protection Product Selector helps match a curb device to your opening.