Help Reverse Your Customers' Bad Flushing Habits

Odds are you've seen an uptick in non-flushable waste in septic tanks since stay-at-home orders began. Here are a few reminders you can offer your customers to keep their systems running smoothly.

Help Reverse Your Customers' Bad Flushing Habits

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Some may think because some homes have a garbage disposal it is OK to just use a toilet to get rid of food waste. And stay-at-home orders have increased this bad habit. Remind your customers that there are several reasons why it is not wise to flush food down the toilet:

1. Plugging of pipes - The food particles could plug the plumbing. Toilets are designed to only receive human waste and toilet paper. The pipes that vacate a toilet are too narrow to handle food scraps, and new toilets use less than 2 gallons of water per flush. The plumbing in the toilet is typically 2 inches in diameter, while most sewage pipes are 4 inches. Food does not break down as easily and quickly as human waste and toilet paper, which are the only two things that should ever be flushed down a toilet. This would be particularly true if a customer has older plumbing such as cast iron and clay, but it can even occur with PVC, particularly if other nonbiodegradable items (i.e., sanitizing wipes) are being flushed. This can result in a backup of sewage in the home. Some of the worst things to flush are:

  • Oils and fats – This includes any food substance that hardens when it cools: bacon fat, butter, lard or cooking oils. These substances congeal inside your sewer lines, constricting sewage flow or stopping it entirely. As cooking fats gather and harden inside pipes, they collect other bits of debris down the line and form large clumps.
  • Hard food scraps that break down slowly – Animal bones, poultry skins, corn cobs and coffee grounds are just a few examples of food scraps that take a long time to decompose.
  • Grains – Rice, oats and other grains swell when they absorb water. When a customer flushes a bowl of oatmeal, the oats can keep expanding and stop up the sewage line.
  • Starchy foods – When starch like rice and mashed potatoes combine with water, it liquifies into a gooey gel that’s hard to push through pipes. 

2. Increased need for tank pumping – The addition of undigested solids will add to the load in the septic tank. The septic tank will likely need more frequent cleaning.

3. Increased load to downstream pretreatment units – Aerobic treatment units or media filters are designed for a maximum organic load, which may be exceeded with the addition of undigested food.

4. Increased load to the drainfield – All soil treatment systems are designed for effluent that has been pretreated in a septic tank and/or an advanced treatment system. As the load increases, the longevity of the drainfield will decrease. 

As can be seen from the list above, it is best if excess food waste does not enter a septic system. Inform customers that this waste is best composted or put in the garbage. Pass along the following tips: 

  • Pour unwanted liquid-based foods like soup or cooking fats into an old can or leakproof plastic bag and toss it in the trash.
  • Almost all food scraps can be composted. See if your city has a compost program and separate your compostable scraps for this purpose. If not, make your own compost pile.
  • Put your smelliest food scraps (fish skins, soggy meat wrappers, etc.) in a plastic bag and store it in the freezer until trash day, when you can add it to your bin and take it immediately curbside for the garbage hauler.

About the author: Sara Heger, Ph.D., is an engineer, researcher and instructor in the Onsite Sewage Treatment Program in the Water Resources Center at the University of Minnesota. She presents at many local and national training events regarding the design, installation and management of septic systems and related research. Heger is education chair of the Minnesota Onsite Wastewater Association and the National Onsite Wastewater Recycling Association, and she serves on the NSF International Committee on Wastewater Treatment Systems. Ask Heger questions about septic system maintenance and operation by sending an email to


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