OWS Maintenance

Your Crew Is Dumping Degreaser Down the OWS

March 2026·8 min read

This happens more often than you think. A manufacturing facility calls because their oil/water separator is not working right. Water is not draining. There is a sheen on the stormwater discharge. The city sent a warning letter. When the technician opens the separator and starts asking questions, the story comes out: the maintenance crew has been pouring degreaser into the floor drains for months.

They were trying to help. The shop floor gets greasy, the drains get slow, and someone figured that a little degreaser would cut through the buildup. Makes sense if you do not know how an oil/water separator works. Makes a very expensive mess if you do.

Liquid splashes from underneath a vehicle onto pavement, spreading across the ground in a small puddle. The surface is wet with the discharge. — A liquid release on pavement during a spill response training exercise (water was used as a fuel analog). In a real shop, fluid moving across pavement toward a floor drain is the moment a bad practice becomes a regulatory problem. U.S. Army photo, public domain (DVIDS 8320651).

Why Degreaser Destroys Your OWS

An oil/water separator works on a simple principle: oil floats, water sinks. Gravity does the work. The baffles and coalescing plates give the oil time and surface area to separate from the water.

Degreaser emulsifies oil. That is literally what it is designed to do. It breaks oil into tiny droplets that stay suspended in water instead of floating to the surface. When you pour degreaser into a gravity separator, you are defeating the only mechanism the separator has. The emulsified oily water flows straight through and into your discharge.

If that discharge goes to the sanitary sewer, your POTW will see elevated oil and grease. If it goes to stormwater, you are sending emulsified petroleum directly to a waterway. Either way, you are in violation.

What a Violation Looks Like

Pretreatment permit violations typically start at $1,000 to $5,000 per occurrence. Repeated violations can escalate to $10,000+ per day. If the discharge reaches a waterway, Clean Water Act penalties start at $25,000 per day. Add in emergency OWS cleaning ($2,500 to $6,000), potential remediation, and legal fees, and a $15 jug of degreaser just became a $50,000 problem.

What To Do Right Now

Stop putting degreaser in any drain that connects to the OWS. If your crew needs to degrease the floor, they need to mop it up and dispose of the mop water as waste, not pour it down the drain.

Get your OWS pumped and inspected immediately. The coalescing plates may be coated and ineffective. The waste from this cleaning may need special characterization.

Label every drain. Put a sign on every floor drain in the facility that says where it goes: "This drain connects to the oil/water separator. No chemicals, solvents, or degreasers."

Train your crew. Not a one-time safety meeting. Actual hands-on training where you show them the separator, explain how it works, and make clear what can and cannot go into the drains. Document the training.

Approved Alternatives

Use a closed-loop scrubber system ($3,000 to $15,000) that captures and recycles wash water. For spot cleaning, use absorbent pads or granular absorbent. Some facilities use bioremediation products that break down oil with bacteria without emulsifying it, but check with your OWS manufacturer and permit authority first.

Bottom Line

An oil/water separator is not a drain. It is a piece of environmental compliance equipment. When your crew dumps degreaser into it, they are creating a discharge violation that starts at $15,000 and goes up fast. Train your people. Label your drains. Get your OWS pumped on schedule.

Need your OWS cleaned or inspected? Check our provider directory or read our OWS maintenance guide.