Your Crew Is Dumping Degreaser Down the OWS: What Happens Next

A facility manager called us because the city had traced oil showing up in the storm system back to his property. He was confused. He didn't have any active spills. No leaking tanks. No obvious source. The city was threatening fines and he had no idea where the contamination was coming from.

After about twenty minutes on site, we found the problem. His maintenance crew had been pouring industrial degreaser directly into the floor drains that fed the property's oil/water separator. They'd been doing it for months. Nobody told them not to, because nobody on the team actually knew how the OWS worked.

This isn't rare. It happens more often than you'd think. And the consequences range from expensive cleanup to five-figure fines.

How an Oil/Water Separator Actually Works

An OWS is one of the simplest pieces of environmental equipment at your facility, and that simplicity is exactly why people underestimate it.

The concept is basic: oil floats on water. An OWS is an underground vault with a series of baffles (walls that don't go all the way to the bottom or top of the chamber). Water flows into the first chamber, slows down, and gravity does the work. Oil and petroleum products float to the surface. The baffles trap that floating oil layer while allowing the cleaner water underneath to pass through to the next chamber and eventually out to the storm drain or sanitary sewer.

That's it. No moving parts. No electronics. Just gravity, time, and baffles.

But it only works under one critical condition: the oil has to stay separated from the water.

Why Degreaser Destroys the Whole System

Degreasers, soaps, detergents, and surfactants all do the same thing from a chemistry perspective. They break surface tension. That's how they clean grease off an engine block or oil off a shop floor. They make the oil mix with water instead of sitting on top of it.

Now think about what that means inside your OWS.

The entire device works because oil floats. Pour degreaser in there and suddenly the oil doesn't float anymore. It emulsifies. It mixes into the water column. And that emulsified mixture flows right past the baffles, right through the separator, and right out into whatever the separator discharges to.

In the case of the facility I mentioned, months of degreaser use had created a steady flow of emulsified petroleum into the city storm system. The oil wasn't separating in the OWS at all. It was passing straight through. The city traced it back using dye testing and catch basin inspections.

What the Cleanup Looked Like

Once we identified the source, the remediation process involved several steps.

First, the OWS had to be fully pumped out and cleaned. Months of accumulated sludge, emulsified oil, and degreaser residue had built up in all chambers. This isn't a garden hose job. It required a vacuum truck, confined space entry protocols, and proper disposal of the contaminated material as regulated waste.

Second, the downstream infrastructure had to be inspected. When oil passes through an OWS, it doesn't just vanish. It coats the interior of storm drain pipes, accumulates in catch basins, and can travel significant distances through the system. Each affected structure had to be cleaned.

Third, the facility needed to demonstrate to the city that the problem was resolved. That meant documenting the cleaning, implementing new procedures, and scheduling regular OWS maintenance going forward.

The total cost was significantly more than a year's worth of routine quarterly OWS cleanings would have been. A regularly maintained OWS might cost $300-800 per cleaning, four times a year. The emergency remediation and city-mandated cleanup ran well into five figures.

How to Prevent This at Your Facility

The fix is surprisingly simple. It's mostly about making sure people know what they can and cannot put down the drain.

Post signage at every floor drain and sink that connects to your OWS. A simple sign that says "No soaps, solvents, or degreasers in this drain" goes a long way. Most crews aren't trying to cause problems. They just don't know.

Train your maintenance staff on what the OWS does. A five-minute explanation during a safety meeting is enough. "This device separates oil from water using gravity. Soap breaks that process. Don't put soap down these drains." That's the entire training.

Schedule regular OWS inspections and cleanings. Monthly visual inspections take about ten minutes. Open the access hatch, look at the oil layer, check the baffles. Quarterly professional cleanings keep the unit functioning properly and create a paper trail that proves you're maintaining it.

Know where your floor drains go. Not every drain in your facility connects to the OWS. Some go to sanitary sewer. Some go directly to storm. You need a site drainage map. If you don't have one, an environmental services company can survey your drains and create one.

Does Your Facility Have an OWS?

If your property has any of the following, there's a good chance you have an oil/water separator somewhere on site: a vehicle maintenance shop, a fueling area, a loading dock with floor drains, a wash bay, or an industrial process that uses petroleum products.

If you're not sure whether you have one, look for rectangular metal access hatches set into the ground near your building, usually in parking areas or near loading docks. They're typically 2-3 feet wide and may be labeled. If you find one and don't know the last time it was serviced, that's your sign to call someone.

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