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Drop Inlet Protection: Sacks, Guards, and Grates | Mainline Materials
Drop Inlet Protection: Sacks, Guards, and Grates
What drop inlet protection is, the devices, and how to choose one
In This Guide
Drop inlet protection is sediment control for drop inlets — the flat storm grates set into parking lots, yards, and low areas where runoff drops straight down into the drain. The most common drop inlet protection is a sack or bag that hangs below the grate to catch sediment, though above-grate guards and framed models are also used depending on flow and traffic.
Quick answer: Drop inlet protection guards flat storm grates, most often with a sack that hangs below the grate to catch sediment while filtered water drains through.
Drop inlet protection using a sack below a flat storm grate.
What is a drop inlet?
A drop inlet is a storm drain inlet with a flat grate at ground level, so runoff drops vertically into the structure below. They are common in parking lots, paved areas, and landscaped low spots. Because water enters from above through the grate, drop inlet protection devices are designed to sit on or hang from the grate.
Drop inlet protection devices
- Drop inlet sacks: open-top fabric bags that hang below the grate to collect sediment, easy to install and reuse.
- Above-grate guards: three-dimensional filters that sit over the grate and handle heavy rain overflow.
- Framed models: add a metal frame for rigidity and strength on heavy-traffic inlets.
- Field grate enclosures: fully enclose a field grate to prevent sediment infiltration.
A field grate enclosure prevents sediment from entering the inlet.
Installation and maintenance
Most drop inlet devices install without rebar, held by the grate itself, so a crew can fit them quickly. Runoff passes through the grate, the fabric filters sediment, and overflow features let water bypass safely in heavy rain. Inspect after each significant rain and remove sediment before it reduces capacity. Reusable models can be emptied and reinstalled.
Choosing drop inlet protection
Measure the grate opening and choose a device sized to it. Standard sacks suit typical drop grates; framed models suit heavy-traffic or demanding inlets; above-grate guards suit overflow-prone locations. The Inlet Protection Product Selector matches a device to your grate.
Not sure which product fits your site? Use the Inlet Protection Product Selector, our free interactive tool under the Resources menu, to answer a few plain-language questions and get matched to the right inlet protection device, type, and size for your storm drain or curb inlet.
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Shop Inlet Protection Use the Inlet Protection SelectorFrequently Asked Questions
What is drop inlet protection?
Drop inlet protection is sediment control for drop inlets — the flat storm grates in parking lots, yards, and low areas. The most common device is a sack that hangs below the grate to catch sediment while filtered water drains through.
What is a drop inlet?
A drop inlet is a storm drain inlet with a flat grate at ground level, so runoff drops vertically into the structure below. They are common in parking lots, paved areas, and landscaped low spots.
What devices provide drop inlet protection?
Devices include drop inlet sacks that hang below the grate, above-grate guards that handle heavy overflow, framed models that add rigidity for heavy traffic, and field grate enclosures that fully enclose the grate.
How do drop inlet devices install?
Most drop inlet devices install without rebar, held in place by the grate itself, so a crew can fit them quickly. Runoff passes through the grate, the fabric filters sediment, and overflow features let water bypass in heavy rain.
How do I choose drop inlet protection?
Measure the grate opening and choose a device sized to it. Standard sacks suit typical drop grates, framed models suit heavy-traffic inlets, and above-grate guards suit overflow-prone locations.