OIL & WATER SEPERATORS
Oil and water separators are large capacity, underground cement vaults installed between a drain and the connecting sewer pipe. These vaults are designed with baffles to trap sediments and retain floating oils while allowing the remaining wastewater to be discharged to the wastewater collection system by gravity. The large capacity of the vaults slows down the wastewater allowing oil to reach the surface and solid material to settle out.
Any business that plans to discharge oily or sediment-laden wastewater to the sewer must install, use and maintain an oil and water separator. Businesses that typically need oil and water separators include:
- Quick lube stations
- Transportation fueling facilities
- Vehicl/heavy equipment repair facilities
- Businesses using steam or pressure washers
Many think that if the separator is still draining, it is working; but like any "filter" an oil and water separator needs occasional cleaning. A separator's efficiency is most affected by settled solids or sludge and by oils. You should inspect the separator at least every six months.
When cleaning:
- Open the inspection plates with a screwdriver and look into each chamber. Make sure the outlet chamber (usually the closest to the street) has a sampling "T". It should have at least a six-inch extension below the water surface.
- Take a long stick that will reach the bottom (about 8 feet). Any resistance to punch through the bottom will indicate a sludge buildup. Service the oil and water separator when the buildup is about 8 inches deep in the inlet chamber (typically the one closest to the drain).
- Measure the oil floating on top of the water. When there are two inches or more of oil in any chamber, it should be removed. Older oil has a chance of becoming emulsified (broken up into smaller droplets).
Who do I call to clean it out?
The yellow pages will list companies that pump out and clean oil and water separators. These firms have special vacuum trucks that pump out materials with the consistency of anything from liquid slurry to solid dirt. The bulk liquid is shipped to a licensed treatment facility where oils, solids and heavy metals are separated from the water. The treated water can be discharged to the sewer. You should never use a septic tank service to clean you oil and water separator or catch basin. Since vendors may have different requirements and/or treatment methods, cost could vary. Fees can include:
- Lab analysis of a sample of the separator's contents
- Wastewater disposal charges
- Surcharge for excessive oil and sludge
- Truck time, figured portal to portal, with a 2-4 hour minimum
- Tank truck rinse out at the treatment facility
What should not go through a separator?
Antifreeze, degreasers, and detergents will emulsify oil into small droplets so the oil doesn't float to the surface. This will allow these pollutants to drain into the sewer system.
Fuels, alcohols, or solvents not only can emulsify oil, but accumulated vapors can pose a threat to line workers at the pump stations or treatment plant.
Concentrated amounts of oily products can overload the baffles or plates and pass through to the sewer.
Floating oils that are not skimmed from the surface of the separator will eventually become emulsified and appear to have a lighter color.
Heavy metal-bearing wastewater such as hot tank and cabinet washer solutions from auto repair shops, any metal finishing, plating, or metal recovery water, and water-soluble machine coolant should not go through a separator also.
What can I do to maintain my oil and water separator?
You can save maintenance costs by diverting oils and sludge out of your separator. The sooner oils are removed, the less chance they will have to become emulsified. Oils that are free-floating can be carefully vacuumed off with a wet/dry vacuum. This oil should be stored in a separate drum and properly disposed of. Cleaners may contain certain chemicals that, when mixed with the oil, could make them a hazardous waste.
Another way to remove oil is to use absorbent pads or socks. These float on top of the water and attract only oil. They can be placed in the inlet chamber to trap oil before it gets a chance to migrate. Pads should be checked often so they don't get saturated. Pads can be wrung out and reused if handled properly and are available at most chemical and safety supply stores.
Sludge is caked-on grease and oil dirt that builds up on the bottom of the separator. It is expensive to dispose of and difficult to clean out. A catch basin, installed before the separator will trap sludge before it washes into the separator. The sludge can then be shoveled out. This can be very helpful to business cleaning muddy equipment. | 
