Environmental Health
Septic Systems
Operation and Maintenance
  Special Conditions  
  Wet Weather or Flooding  l  Power Outages  l  Infrequent Use & Other Conditions  

There are many conditions that can impact your septic system (on-site sewage system), like flooding, power outages, and infrequent or more frequent use. During these circumstances, the limitations of your on-site sewage system can pose health concerns unless certain precautions are taken.

Wet Weather or Flooding

Excessive water in the drainfield causes the septic system to overload, slowing down or stopping the treatment of wastewater. When this occurs you run the risk of your septic waste backing up into your home, particularly if your drainfield is partially clogged. Although it may work well during dry weather, in wet weather, a rain-soaked drainfield may be too saturated for the effluent to percolate down through the soil. To understand how the drainfield works, see The Drainfield.

During flooding or heavy rains, it is prudent to reduce, and in some cases, stop using your septic system. If you are affected by the threat of flooding, there are certain things you can do during a major rain or flood:

  • Conserve water usage and reduce toilet flushing until the system is restored to working order.
  • If your drainfield is covered with water, do not use the system until the water has receded.
  • If you have a pump, turn off the electricity.
  • Make sure there is no damage to electrical connections before turning the system back on.
    NOTE: Be sure to turn the pump on before using the system.
  • If silt and debris have gotten into your septic tank, have the system pumped as soon as possible. NOTE: Wait until the water has receded and the area is no longer saturated before opening the tank.
  • If any sewage has backed up into the house, avoid contact with it. Disinfect thoroughly to prevent serious illness from the disease-causing organisms in the wastewater.
  • Check for blockages. It is possible the outlet tee (or baffle) may be partially plugged due to floating scum that floated up during the flooding.
  • If you use a well for drinking water and flooding came up to the well casing, do not drink the water. If the water is murky, have it tested before drinking (see How to Collect a Water Sample).

Contact a septic system professional, if any of the following problems are present:

  • Water over the drainfield that does not recede after the rain stops.
  • You smell a sewage odor.
  • Wastewater or sewage backs up into the house.
  • Slow running drains, especially after doing laundry or taking a shower.
  • You notice soggy areas with surfacing sewage in your yard.

For additional information, see Septic Systems, What to Do After the Flood, U.S. Environmental Protection Agency.

Power Outage

Unless you have a gravity septic system (which does not require electricity and continues to operate efficiently even when the power is off), most other systems are dependent upon electricity to run the pump or other electrical components.

  • Keep water use to a minimum, especially if the system has a pump. The septic tank can hold about one-day's supply of waste. Once the tank is filled, additional waste can back up into your home.
  • Turn off the pump at the control panel. Effluent will continue to build up in the pump chamber until it resumes operation.
  • After power is restored, switch the pump on and let it run for 5 minutes maximum; turn it off again.
  • Repeat this manual switching every 6 hours until the effluent drops to the "OFF" float level and the pump turns off automatically. If there is little water use during the outage or pump service, the pump may automatically turn off during the first manual switching.

CAUTION: Do not enter the pump chamber. Gases inside pump chambers are poisonous and the lack of oxygen can be fatal. Always turn off the power supply at the circuit breaker, and unplug all power cords before handling the pump or floats. The service or repair of pumps and other electrical equipment must be done by an experienced person.

Infrequent Use and Other Conditions

Infrequent use (such as vacation homes) may not keep enough waste in the system to give the bacteria enough food to sustain themselves. Use the toilet a few times to allow the microbes enough time to rebuild themselves before doing laundry or other high-water usage activities.

Other conditions that put added stress on the system include the arrival of an infant or extended holiday visits from relatives or friends. Reduce water load during these times.

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Use Water Efficiently

Replace existing toilets and shower heads with low-flow units

Repair leaky fixtures

Wash clothes and dishes only when you have a full load

Take shorter showers

Don't let water run while brushing teeth, dishes, etc.

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This page last updated: 03/30/18