Water Resources Center

The Water Resources Center is affiliated with the College of Food, Agricultural and Natural Resource Sciences and University of Minnesota Extension.

Septic System Failures

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Sewage from homes has pathogens such as bacteria and viruses, plus nutrients, solids and cleaning products that can cause human health and environmental problems. "Failure" of a septic system means that wastewater may be allowed to come in contact with people or enter the natural environment before it is harmless.

Common indicators of a failing or failed septic system may include one or more of the following:

  • Sewage backup into the house.
  • Water or sewage surfacing in the yard or a ditch. Sewage odors indoors or outdoors.
  • High levels of nitrates or coliform bacteria in well water tests.
  • Alarms sounding/flashing on the system.
  • Frozen pipes or soil treatment areas.
  • Frequent intestinal disorders.
  • Algae blooms and excessive plant growth in nearby ponds or lakes.

Failure to properly treat sewage is most commonly the result of: improper design, installation or sizing of one or more components of the system; over use of water in the household; or lack of proper maintenance.

Improper design, installation, or sizing may be a result of mistakes by the professionals when the system was installed. More commonly, it means that the wrong system was chosen for the site and soil conditions (i.e. high water table, cesspool, etc.); or the residence was been modified to include more people or use fixtures or appliances that the system was not designed or sized to handle. Examples of this are a bedroom addition to the house or the installation of a garbage disposal.

Over-use of water is a common problem since the typical person (man, woman, or child) uses about 100 gallons of water per person per day. Systems are sized for normal volumes of water use, but abnormally high usage or accidental over-use - leaky fixtures - can easily overload a system. And partially damaged drainfield (perhaps from improper maintenance) may not be able to treat even normal water use rates. This situation often occurs when a home of one or two persons is sold to a family of five or six and water use suddenly increases.

Improper maintenance -- the solids that accumulate in the septic tank must be removed regularly. Build-up of excessive scum or sludge in the tank will cause solids to enter the soil treatment area and plug it over time. The University of Minnesota Extension Service recommendation suggests a septic tank should be cleaned (pumped) through the manhole every one to three years to remove all of the solids. The frequency of cleaning depends on several factors including the number of people in the home, the size of the tank and garbage disposal usage. The removal of all solids requires flushing and back flushing of the tank several times

By following some simple home management and maintenance practices, these failures can be eliminated.