Storm Drain Filters: How to Choose the Right One for Your Inlet
Quick Answer
Pick a storm drain filter by the type of inlet and the pollutant you need to catch. For a grate in a parking lot or yard, either hang a drain guard under the grate or lay a filter on top of it, like a magnetic Inlet Guard Plus or a Grate Guard. For a curb opening, use a curb guard, a gutter guard or filter socks across the face. For a pipe outlet, strap a pipe sock on the end. Sediment only needs a sediment filter; oil sheen needs an oil absorbing fabric; dissolved metals like zinc and copper need heavy metal media. Whatever you pick, inspect it after every storm and clean or replace it before it fills up.
Why storm drain filters matter
EPA calls inlet protection "often the last opportunity" to treat stormwater before it leaves your site. It is a backup, not your main sediment control, so it works best alongside good housekeeping and erosion control upstream. On construction sites covered by EPA's 2022 Construction General Permit, Part 2.2.10 covers protecting storm drain inlets. Industrial sites under the Multi Sector General Permit have to pick, install and maintain stormwater control measures in their SWPPP. Your state permit may word it differently, so check what yours asks for.
General information, not legal advice. Your permit and SWPPP set the actual requirements.
Match the filter to the inlet
| Inlet type | Filter options | Good to know |
|---|---|---|
| Grate inlet or catch basin | Drain guard under the grate; Grate Guard over the grate; Inlet Guard Plus on top | Under grate guards hide from view; on top filters keep everything at street level for easy cleanup |
| Curb opening | Curb Guard Plus; Gutter Guard Plus; Inlet Guard Plus curb style; filter socks | Low profile curb guards hold up better to street sweepers |
| Pipe outlet | Pipe sock | For non corrugated discharge pipes |
| Downspout, channel or flat area | Filter socks | Lay them in front of the flow, no hardware needed |
Grate inlets: under the grate or on top
Drain guards hang inside the catch basin, pinched in place by the grate. The Oil & Sediment models catch silt and soak up oil, and overflow ports pass heavy rain so the street doesn't flood. Water that goes through the overflow is untreated, so keep the guard clean. See our drain guard guide for sizes, install and maintenance, or shop all drain guards.
Grate Guard. The Grate Guard, Sediment Only, 24" x 24" x 4", Part #9273-SED wraps over the grate and closes with a hook and loop flap. Once it's on you don't lift the grate again, and debris stays at street level. The black fabric shows, so it's not the pick where looks matter.
Inlet Guard Plus. About the easiest stormwater product there is to install: no grates to lift, no fabric to pinch, no cutting. Line it up with the grate, lay it down, and the sewn in magnets hold it. Cleanup is sweeping off the top. It has to match the drain size closely, and it is more exposed to street sweepers and theft. Grate only sizes come in 2' x 2', 2' x 3' and 2' x 4', like the 2' x 2' grate only model, Part #9160.
Curb inlets
- Curb Guard Plus, 3 ft, Part #9248 and 4 ft, Part #9251: low profile foam wedges that sit across the curb opening, made with Ultra-Filter-Tex to soak up oil and other hydrocarbons. UltraTech lists flow at 28 GPM for the 3 ft and 37.3 GPM for the 4 ft. Cut to length for a custom fit.
- Gutter Guard Plus, 6" x 6', Part #9151: a framed sediment barrier with a back pouch you fill with rock or rebar as counterweight. Sediment, dirt and debris only; it won't remove oil or metals. Takes more time to set up than the others.
- Inlet Guard Plus curb style, Part #9163, plus 2' x 3' and 2' x 4' sizes, for curb inlets with a grate.
Filter socks: pick the media for the pollutant
Filter socks are 9 ft tubes of filter media. Lay one in front of a drain or across a runoff path; no hardware and no grates to lift. Overlap socks for longer inlets, and stack different media in a "treatment train" when you have more than one pollutant.
- Sediment, Part #9457 (bulk 36 pack, Part #9459): silt and solids.
- HMRM 1.0 heavy metal, Part #9454: dissolved metals. UltraTech's data sheet lists zinc, copper, lead, cadmium and more, and rates a 9 ft sock at 1,145 grams of metal removed (actual results vary with concentration and flow). Rinse it on grass before first use to knock off media dust.
- Sorb 44, Part #9455: oil and hydrocarbons.
- PhosFilter, Part #9456: phosphorus.
- Carbon, Part #9453: activated carbon.
Socks can be a trip hazard and can get in a sweeper's way, so place them with that in mind.
Heavy metals at a catch basin
If sampling keeps flagging metals at one drain, the HydroKleen Heavy Metal Media Filter Bag, Part #9460 sits inside the basin and holds up to three filter media, with activated carbon usually last as a polishing step. UltraTech rates its heavy metal capacity at 285 grams. A round basin needs at least a 26 inch opening. Ask us before ordering so we can match the frame and media.
Pipe outlets
The Pipe Sock, Oil & Sediment, for 12" pipe, Part #9706-OS straps over the end of a non corrugated discharge pipe. It lets water through while soaking up petroleum, animal and vegetable oils, up to 2.6 gallons for the 12 inch size. 8 inch and 16 inch sizes are available too.
Keep them working
- Check every filter after each storm. EPA's inlet protection fact sheet calls for checking controls after each storm event.
- Clean out sediment when the filter's capacity is down by about half (EPA's guidance for settling areas). A clogged filter can push water around the inlet and erode the ground next to it.
- Replace torn fabric right away.
- Swap oil soaked filters instead of reusing them.
- Keep spares on site. Stormwater filters are consumables, so plan on reordering on a schedule instead of waiting for one to fail.
How to pick in 30 seconds
- Parking lot grate, oil and sediment: Oil & Sediment drain guard under the grate.
- Grate you never want to lift again: Grate Guard or Inlet Guard Plus on top.
- Curb opening on a street or lot: Curb Guard Plus.
- Construction site, mostly mud: sediment filter socks or Gutter Guard Plus.
- Zinc or copper in your samples: HMRM 1.0 socks or a HydroKleen Heavy Metal bag.
- Discharge pipe: pipe sock sized to the pipe.
Get a stormwater quote
Tell us how many inlets you have, what type (grate, curb, pipe), the grate or opening size, and what your permit or sampling is targeting. We'll put the full list together and quote shipping to your site. Stormwater items are usually in stock and arrive in about 7 to 10 business days. Email orders@industrialandsafetysupply.com or use the button below.
Frequently Asked Questions
What is the best storm drain filter?
It depends on the inlet and the pollutant. Drain guards suit catch basin grates, curb guards suit curb openings, pipe socks suit pipe outlets, and filter socks work almost anywhere. Choose sediment, oil or heavy metal media based on what you need to remove.
How often should storm drain filters be inspected?
After every storm, plus whatever schedule your permit sets. Clean out sediment when capacity is down by about half and replace torn or oil soaked filters.
Do storm drain filters remove oil?
Oil & Sediment drain guards, Curb Guard Plus, pipe socks and Sorb 44 filter socks are made to absorb oil and hydrocarbons. Sediment only products like the Gutter Guard Plus and reusable drain guards do not.
Can a storm drain filter remove heavy metals?
Yes, with heavy metal media. The HMRM 1.0 filter sock and the HydroKleen Heavy Metal bag use media rated for dissolved metals such as zinc and copper. Results depend on concentration and flow.
Will a storm drain filter cause flooding?
A clogged filter can back water up or push it around the inlet. Many models have overflow ports for heavy rain, but water through the overflow is untreated, so keep filters clean.