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Fats, Oils & Grease (FOG)

Sanitary sewer systems are designed to handle three types of waste products: used water; human body waste; and toilet paper. They are not designed to handle other waste products that are sometimes disposed of improperly.

Don't Pour Grease Down the Drain!

Grease gets into the sewer from household drains and from poorly maintained grease traps in restaurants and other businesses. Too often, grease is washed into the plumbing system, usually through the kitchen sink. Grease sticks to the insides of sewer pipe (both on your property and in the streets). Over time, the grease can build up and block the entire pipe.

Home garbage disposals do not keep the grease out of the plumbing systems. These units only shred solid material into smaller pieces and do not prevent grease from going down the drain. Commercial additives, including detergents that claim to dissolve grease, may pass grease down the line and cause problems in other areas of the sewer system.

When grease is poured down sinks, it can solidify and cause sewer backups into houses or onto streets. The result is a greasy, smelly mess of pollutants entering storm drains, creeks and the San Francisco Bay. It harms wildlife both on land and in water. It is also is expensive to clean up!

Best Practices

To ensure this system works properly, here are some best practices to follow.

Do Not

  • Do not pour fats, oils and grease from cooking down the kitchen sink drain or garbage disposal.
  • Do not use the sewer to dispose of food scraps.
  • Do not use the toilet as a wastebasket for garbage or chemicals. These items can kill beneficial bacteria used for sewage treatment, cost much more to treat and can enter the Bay.
  • Do not put produce stickers down the drain.
  • Do not plant trees with shallow, spreading root systems near your sewer lateral. Tree roots seek water sources, such as cracked sewer lines. Once the roots penetrate the line through the cracks, the roots can create a dense mat and trap materials.


  • Collect grease in a container and dispose of it in the garbage.
  • Place food scraps in the garbage for disposal with solid waste, or start a compost pile.
  • Place a wastebasket in the bathroom to dispose of solid waste. Disposable diapers and personal hygiene products do not belong in the sewer system.