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Public Health - Seattle & King County

What to do during a power outage

One of the first things you need to do when the power fails is to be water wise. Why? Because pump systems are dependent on electricity to move the effluent (liquid sewage from the septic tank) into the drainfield.

WARNING:
If you continue to use water by flushing toilets, washing dishes, or even taking showers, the septic tank continues to fill. When effluent doesn't get pumped to the drainfield, the pump tank becomes full and effluent may back up into the house!

Simple ways to be water-wise during a power outage:

  • Take short showers
  • Don't wash laundry
  • Don't let the water run while brushing teeth, shaving or rinsing dishes
  • Don't flush the toilet each time it's used for liquid waste

If your septic system has a pump, what you do next depends if the pump is “on demand” or if it has a "timer."

On-demand pump system:

An on-demand pump system is the most common kind of pump system. The on demand pump begins its pump cycle whenever the wastewater volume reaches a premarked level in the septic tank, and the effluent (liquid sewage from the septic tank) is pumped into the drainfield.

When there is a power outage, the effluent is not being pumped into the drainfield. The septic and pump tank will collect the wastewater throughout the power outage, and release it all at once when the power is restored and the pump starts working. Too much water pumped into the drainfield will flood the drainfield and cause complications.

What can you do? Follow these 3 steps and become a human timer:

  • Turn the circuit to the pump 'off' while the power is out.
  • When the power is restored, turn the pump 'on' for 2 minutes and 'off' for 4 – 6 hours. You are now "dosing" the right amount of effluent into the drainfield over a given period of time. If there was little water use during the power outage, the pump may automatically turn off during the first manual dosing.
  • Conserve water and continue the 2-minute pumping every 4 – 6 hours until the pump turns itself off.

Timer:

A pump system with a timer controls the number of times the pump starts and stops. It manages how much effluent (liquid sewage from the septic tank) goes into the drainfield in a 24-hour time period. Timers make sure that the drainfield only gets as much effluent as it was designed to handle. The timer system will eventually take care of itself once the power is restored. If your system has a timer, it may be indicated on the as-built (scaled drawing of the septic system). It is usually found on a wall or post near the pump tank or in the garage.

What can you do? If the power has been off for awhile, the timer will be behind. In order to let your timer catch up, continue to conserve water for an additional day or more.

  • Take short showers
  • Don't wash laundry
  • Don't let the water run while brushing teeth, shaving or rinsing dishes
  • Don't flush the toilet each time it's used for liquid waste

If the high water alarm sounds when the power is restored, the effluent has backed up into the reserve storage area of the pump tank. Refer to Steps 1-3 under the on-demand heading to start pumping the backed up sewage to the drainfield.