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Septic tank systems during power outages or floods

Septic tank systems during power outages or floods

Power outages

  • Reduce your water use to a minimum, especially if the system has a pump. If all the reserve storage inside the chamber is used, the waste pipes in your home can back-up. There is usually a one-day supply of emergency storage space available in the pump tank.
  • Turn off the pump at the control panel.
  • WARNING: If the power outage caused the pump to malfunction, do not enter the pump chamber. Gases inside pump chambers are toxic and can be fatal. It is best to call a certified septic system installer for service or repair.
  • After power is restored, switch the pump on and let it run for a maximum of 5 minutes, and then turn it off. Repeat this manual switching every 6 hours until the effluent drops to the "OFF" level and the pump turns off by itself. If only a small amount of water was used, the pump may automatically turn off during the first switching.
  • CAUTION: When repairing the pump, always turn off the power supply at the circuit breaker and unplug all power cord before handling the pump or floats.


  • Septic tank systems that have been flooded should not be used (e.g. do not flush your toilet).
  • Make sure you turn off power to the septic system and all cords are unplugged before inspecting the area.
  • After waters have receded, check the system for broken lines or sewage surfacing.
  • Consult with a septic system service professional to inspect and repair your system.
    • Reduce water use until the system is inspected and repaired.

Visit the Public Health Wastewater Program to learn more about onsite septic systems in King County.