Stormwater Drain Guards vs. Filter Socks vs. Catch Basin Filtering Systems

If there are stormwater drains present in or around a construction site, an industrial facility, or even vehicle storage or parking area, those drains must be protected to prevent local drinking water supplies and the larger surrounding area’s watersheds from being contaminated by sediment and other pollutants.

There are a number of products designed to help filter pollutants out of stormwater before it passes through the drain and into the stormwater system. Two of the more popular options are drain guards and filter socks. One of these is installed below the drain; one above the drain. The first is quite a bit more expensive than the second but also provides more effective (and flexible) filtering.

There is also a third alternative, far more capable but also more expensive. We’ll discuss catch-basin filtering systems later in this article.

Drain Guards -- Out of Sight, Not Out of Mind

Several companies manufacture and sell stormwater drain guards. Some but not all of these guards are engineered to remove contaminants like litter, sand, and oil from stormwater flow before it pollutes rivers, streams, and groundwater resources.

The most effective stormwater drain guards are made of a geotextile fabric that filters out a variety of sediments and pollutants, depending on the model. For example, our own Ultra-Drain Guard offers three integrated features that offer separate benefits -- the removal of sediments and oils, antimicrobial action in storm sewer retention pools/sumps, and compliance with EPA National Pollutant Discharge Elimination System (NPDES) requirements 40 CFR 122.26 (1999) when used as Best Management Practice in Stormwater Pollution Prevention Plans.

Installing a drain guard is a simple matter. Just lift the storm sewer grate and drop the fitted drain guard into place. The weight of the grate holds it there firmly, and permits easy removal when it has reached its holding capacity. This makes it ideal for use in industrial facilities, construction sites, and even parking lots where stormwater runoff is likely to carry oil, eroded soil, debris, and fuel contaminants from cars.

But in some situations -- particularly those where high levels of sediment can quickly clog a drain guard -- you might find other solutions more appropriate.

Filter Socks -- Easily Installed and Monitored

These products are perhaps the most familiar stormwater mitigation method to many people, because they’re placed in plain sight around and near stormwater drains. They resemble “draft dodgers” -- energy-saving devices placed at door thresholds to prevent air from infiltrating residences -- but have a much more high-tech filling, which absorbs pollutants including oil, fuel, chemicals, heavy metals, and others to help comply with EPA regulations. They also capture sediment, but don’t fill up like drain guards, and so can require less intensive checking and reduce frequent replacement.

Filter socks like our Ultra-Filter Sock work by using a porous textile exterior that permits water to flow into storm drains, while an absorptive media filling holds back a variety of chemicals ranging from hydrocarbons (oils) to phosphorous (commonly found in fertilizers) to poisonous heavy metals -- all of which can result in damage to wetlands and inland waterways. These filters are generally made of UV-resistant outer layers to stand up to full-time exposure to the sun. Installation is as easy as dropping them into place to form a wall around the stormwater drain, and they’re easily monitored because they remain at street level.

The single most unique element of the Ultra-Filter Socks is their ability to remove such a diverse variety of pollutants with ease. No other passive stormwater system has this level of flexibility combined with such simple installation.

However, in circumstances where the level of sediments is extreme, or where the toxicity of pollutants that must be removed is high, these low-tech, passive methods might not be enough. That’s when it might be necessary to enhance removal with a catch-basin filtering system.

Hydrokleen: High Performance for High-Pollutant Installations

Circumstances where sediment runoff and dissolved pollutants exceed normal levels demand catch-basin filtering systems that offer higher capacities and greater performance. UltraTech’s Ultra-Hydrocleen system is considered a “true filter” by the EPA since this complex (yet ingeniously simple) device directs water through several separate filtration media before releasing it into the stormwater drain.

The mix-and-match ability of the Hydrocleen system permits users to choose the right type of filtration for the pollutants present in any given situation. Hydrocarbons, sediments, heavy metals, phosphates, you name it, this patented device deals with them all. Stormwater enters through an initial medium that mitigates sediments and then flows through specialized filtration media as needed. The media choice is customized depending on what pollutants need mitigating. The ability to customize Hydrocleen is unsurpassed, and there’s even a unique “sampling” port that permits users to remove lab specimens of treated water to verify the condition of the filtration media and to prove adherence to regulations concerning the purity of stormwater being released back into local waterways.

Yes, this system costs more than drain guards or filtration socks. But the cost of fines assessed by the EPA and state departments of environmental quality can more than justify the use of a catch-basin system. Consider the recent case of a building contractor fined nearly $70,000, in part for failing to use proper systems to wash out concrete-setting tools, and permitting caustic runoff to pollute the local groundwater.