Floor Drains

Floor drains are collection points which remove wash water and other liquid wastes from a work area and carry them away through pipes or ditches for disposal. Every year Mainers improperly dispose of thousands of gallons of pollutants through floor drains -- a practice which contaminates soil and ground water, threatening drinking water supplies. If your business has floor drains, here are four steps to help you evaluate their risk and identify options to fix this environmental hazard.

STEP 1:  Find out where your floor drains go.
STEP 2:  Know what goes down your floor drains.
STEP 3:  Make the right floor drain connection.
STEP 4:  Notify the DEP.


STEP 1: Find out where your floor drains go. 

Have you checked your floor drains lately? Do you know where they go? If you are unsure where your floor drains go, check the building's blueprint or speak with your local code enforcement officer about conducting a dye test. Identifying where your floor drains are connected is a vital first step.

Floor drains connected to a municipal sewer system are the DEP-preferred connection option. If your floor drains are connected to a municipal sewer system, make sure your local sewer district knows what types of liquid wastes could enter your floor drains. Your local sewer district may require you make an effort to keep some types of pollutants from entering the drains, possibly by developing a spill prevention and containment plan or installing an oil/water separator.

But, not everyone has access to a municipal sewer system. Without access to a municipal sewer, acceptable connection options are limited by the types and amounts of liquid wastes potentially flowing to your floor drains.

STEP 2: Know what goes down your floor drains.  top

Is that just soapy wash water from your vehicles or does it contain gasoline, oils and cleaning solvents? Are process chemicals lost when equipment is cleaned or solutions changed? Thinking about what goes down your floor drains may give you a little headache now, but it's better than the BIG financial and public relations headache that could await you if liquid wastes from your floor drains pollute local drinking water. Consider not only what you know goes down floor drains but also what might drip, leak, spill or wash into them.

Generally, liquid waste can be divided into two broad categories based on its potential to contaminate ground water:

  • LOW RISK - This is waste water that a normal household would produce, including animal and vegetable matter, soap and diluted domestic-use cleaning solutions. Waste water from commercial and industrial sources is also considered LOW RISK as long as both the ingredients and their concentrations are similar to household waste water. Businesses which typically produce this kind of waste water include restaurants, schools, hotels and some veterinary clinics. LOW RISK wastewater also includes wash water solely from the exterior of cars and light trucks, snowmelt from vehicles, and most non-contact cooling water.
  • HIGH RISK - This waste water has ingredients, in types or concentrations, which you would not normally find in household waste water. This category includes waste water which contains any pollutants such as those listed below.

Type of Business

Potential Pollutants to Floor Drains

Engine and equipment repair facilities (vehicles, aircraft, watercraft, etc.)

Various fuels, oils, degreasers, hydraulic fluids, cleaning solvents, antifreeze, metal waste

Printers and silk screening operations

Inks, dyes, cleaning solvents

Photo processors

Spent film developing solutions containing silver, high ammonia wastewater

Commercial car and truck washes

Oil- and grease-contaminated wash water

Dry cleaners

Dry cleaning solutions

Meat packing and food processing facilities

Animal by-products, pathogens, high nitrogen wastewater

Metal fabricators, metal platers and electronic parts manufacturers

Oils, solvents, caustics, paints, metal waste

Pest control companies, lawn care companies and other commercial application services

Pesticides, fertilizers and pesticide-contaminated wash water

Drinking water treatment plants

Caustics, filter backwash containing high concentrations of iron, arsenic or radionuclides

Even if the liquid waste entering your floor drains is LOW RISK, but a significant potential exists for any pollutants to drip, leak, spill or wash into the floor drains, you must consider your liquid waste as HIGH RISK.

STEP 3: Make the right floor drain connection.  top

If you have LOW RISK liquid waste entering your floor drains, here are your options where no municipal sewer is available.  If municipal sewer service is available, the DEP strongly encourages you to contact your local sewer district about connecting the floor drains to the system before pursuing one of these options.  

Option 1: Connect your floor drains to an approved subsurface disposal system. Floor drains may be connected to a subsurface waste water disposal system designed and installed in accordance with the Maine Subsurface Waste Water Disposal Rules (State Plumbing Code) if the following criteria are met:

  • the disposal area is properly sized to handle the potential flow from the drains;
  • there is no significant potential for pollutants to drip, spill or wash into the floor drains; and
  • the floor drain is necessary for the disposal of wash water or other liquid waste similar to household waste water.

Under some circumstances, floor drains discharging LOW RISK wastewater to a subsurface system must also be registered as a UIC Class V well.  Click here for more information about the UIC Program and Class V well registration.

Option 2: Connect your floor drains to a pipe which discharges on top of the ground. Floor drains may be piped to the top of the ground if these criteria are met:

  • the pipe must discharge on top of the ground in an area that is accessible for inspection;
  • the pipe must not discharge directly into a ditch, stream, wetland, pond or other surface water body;
  • there is no significant potential for pollutants to drip, leak, spill or wash into the floor drains; and
  • the volume of liquid waste does not exceed 60 gallons per day, and proper erosion control methods are used for discharge volumes over 30 gallons per day.

DEP recommends the installation of an oil/water separator if snow melt or waste water is generated from cars, trucks or other equipment utilizing engines which run on gasoline, diesel or aviation fuel. However, oil/water separators work best when they receive only oils and water. Water-soluble solvents and some gasoline additives will pass through an oil/water separator and be discharged with the water. Some detergents will also emulsify the oil and allow it to pass through the separator as well. Finally, oil/water separators must be inspected and cleaned routinely, and the waste generated from cleaning the separator must be disposed of in an approved manner (see HIGH RISK, Option 2 discussion).

If you have HIGH RISK liquid waste entering your floor drains or if the potential exists that it could, you have the following options in areas where no municipal sewer is available. Again, if municipal sewer service is available, the DEP strongly encourages you to contact your local sewer district about connecting the floor drains to the system before pursuing one of these options.

Option 1: Seal the floor drains. Ask yourself: Are the floor drains really needed? Floor drains should be avoided or eliminated where possible. A bag of cement, a little water, a trowel -- and you're on your way.

Option 2: Connect to a holding tank. A holding tank is a water-tight vessel, designed and constructed to facilitate ultimate disposal of wastewater at another site.  Holding tank wastewater must be analyzed prior to disposal and the contents of the holding tank disposed of as determined by the laboratory analysis. Proper disposal may mean having the tank contents trucked away as hazardous or special waste by a licensed transporter or, after getting approval from the sanitary district, shipped to a licensed wastewater treatment plant. Additional information about holding tanks.

Option 3: Separate the facility into two areas by building a berm. All activities which could create HIGH RISK liquid waste would be performed in an area where floor drains are sealed or connected to a holding tank. The other area -- the LOW RISK wastewater area -- could be served by floor drains providing certain criteria described above are strictly met. This is appropriate for many fleet maintenance buildings -- the HIGH RISK wastewater area is used for changing fluids and repair work and the LOW RISK waste water area is used for vehicle washing or catching melt-water prior to servicing. Appropriate activities in each area need to be strictly observed and you should have a spill prevention, control and clean-up plan in case HIGH RISK pollutants accidentally make their way into the LOW RISK area.

Option 4:  Obtain a waste discharge license for subsurface disposal of wastewater.  Businesses that generate a significant volume of HIGH RISK waste water and for whom the above options are not practical must obtain a waste discharge license from the DEP for the installation, operation and maintenance of a subsurface waste water disposal system. Examples of such businesses include commercial car washes, meat packing facilities, food processors, drinking water treatment plants and commercial agricultural operations. More information about waste discharge licenses or contact Gregg Wood at DEP, e-mail gregg.wood@Maine.gov, telephone: (207)287-3901.

STEP 4: Notify the DEP.  top

Whether you've sealed your floor drains with cement, connected them to a holding tank or chosen one of the other options mentioned here, you must notify the DEP in writing about your action. The DEP uses information about floor drains to assess potential threats to ground water quality. The steps you take to eliminate or modify risky floor drain practices should be noted by us! 

The UIC Program also requires business owners to notify the DEP thirty (30) days prior to closing floor drains in motor vehicle repair areas (also known as Class V Motor vehicle waste disposal wells).  

Please send closure and/or pre-closure notification to:

Underground Injection Control Program
Maine Dept. of Environmental Protection
Bureau of Land and Water Quality
17 State House Station
Augusta, ME  04333-0017

Fax:  207-287-7191

Contact: Division of Water Resource Regulation, 207-287-3901

Description  Photo
Image: Hydraulic fluid spill covered with absorbent material a little too late. An unknown quantity of hydraulic fluid made it down the floor drain (bottom center of photo) image:  spill into floor drain

Image: hydraulic fluid discharging to a floor drain.

Hydraulic fluid discharging to a floor drain.