Rules for Winter Septic Tank Pumping

Rules for Winter Septic Tank Pumping

In general, pumping septic tanks is not recommended in cold climates during the winter months. Winter’s arrival can vary year to year, but a good rule of thumb in Minnesota, for example, is to avoid pumping from November to April. Below are the most common problems associated with winter pumping.

1. Depending on the size of the family living in the home, it could take days or even weeks for the septic tank(s) to fill back up. The typical person uses approximately 60 gallons per day. If two people were living in a home, it would take eight days for the tank to be full. During these eight days, no wastewater would be traveling out through to the septic tank and out to the soil treatment system. This could result in your septic soil treatment area freezing and your septic tank requiring pumping out for the rest of winter.

2. Often the lids on septic tanks are buried, and once frost gets into the soil, it’s difficult to dig down to the lid. On a side note, it is recommended that these lids be extended to grade to facilitate pumping. Septic tanks can only be properly maintained by accessing the lid. Newer septic tanks have maintenance lids to grade that are insulated. Shallow tanks should be insulated too, as shown in the picture above.

3. If you pump septic tanks and typically land-apply the septage versus taking it to a wastewater treatment plant, it may be more challenging or not allowed if the soil is frozen.       

4. It takes time to get the bacteria up to full speed after a tank pumping. This will happen more rapidly in warmer conditions. In addition, they do not work as well when they are cold, which is more likely after pumping. 


Although winter pumping is not generally recommended, there are a few instances when it may be the correct course of action:

  1. If there is an emergency related to the septic system that involves sewage backing up into the home or sewage coming to the surface in the yard, or if the septic pump needs replacement. 
  2. If a cabin or home sees limited use during the winter, the septic tank can be pumped and then gradually filled over the winter with no wastewater leaving the septic tank. If the tank is located in an area with a high water table, tank buoyancy should be evaluated prior to pumping the tank. If a septic tank is left full with low uses over the winter months, the sewage will get very cold and can even freeze.

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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