Published on April 17, 2020

Imagine waking up in the early morning and stepping out onto your back porch with a hot cup of coffee, steam rising lazily into the air. You stare into the distance, a dense fog lightly hanging over the trees. There is a peaceful and surreal quality about your surroundings. You take a deep breath to relax into the moment…but what you smell is not relaxing. What you smell is a backed-up sewer line, and that backup was caused by another type of FOG that consists of Fats, Oils, and Grease. Your serene morning is now filled with a horrible smell and the possibility of an expensive plumbing bill. Let’s talk about how to prevent sewer backups caused by FOG.


For 13 years I worked as a pretreatment and pollution prevention technician in the water quality department at HRSD. One of the aspects of my job was to visit local restaurants and ensure they were cleaning out their grease traps regularly to prevent grease from building up in the sewer pipes and causing a sanitary sewer overflow. The excuse I heard the most for infrequent cleaning was, “we don’t use grease!” What many people do not realize is grease is not the only problem…FOG is the problem. Fats, Oils, and Grease are comprised of many things including meat fats, lard/shortening, butter/margarine, food scraps, dairy products, batters and icing, and dressings and sauces1. Excessive use of a garbage disposal can also cause buildup in the pipes as it allows for food scraps to go down the drain.  All of these things should be disposed of in the trash.




Why can’t liquids like oil and sauces be poured down the drain?


Once those liquids cool and sit for a while, what happens? They thicken! Over time, those layers of grease, oil, dressings, fats, and butter can build up inside your sewer pipes and can prevent other things from going down…like pee, poo, and toilet paper. If those things cannot continue down the sewer pipe because of a blockage caused by FOG buildup, that pee, poo, and toilet paper will keep piling up inside the sewer pipe and can cause a sanitary sewer overflow. If the buildup is in the sewer pipe in the street (where the sewage from multiple homes and businesses flows), that overflow can happen in the street where people drive, walk, and ride bikes. No one wants to ride through a puddle of sewage! If the buildup occurs in the sewer pipe connected to your house, that sewer backup can cause an overflow in your house by overflowing in your sink or toilet or anything that is connected to a drain. That is certainly not a fun way to start your day!


Photo from


What can you do to reduce FOG in the sewer system?  

  1. Put used cooking grease into a heat-safe container (like an empty tin can). Once the grease solidifies, throw the can into the trash.
  2. Wipe all dishes, utensils, pots, and pans with a paper towel to absorb the grease before washing the used dishes. Toss the soiled paper towel into the trash.
  3. Scrape food scraps into the trash. A strainer can also be placed in your sink to catch the scraps before they go into the drain, and that strainer can be emptied into the trash as well.


Doing your part to keep FOG out of the sewer system not only keeps your sewer pipes free from buildup, but it also helps keep FOG buildup out of the main sewer lines and treatment plants. Each person can make a difference!

  1. “Fat Free Drains,” askHRgreen, 2020,