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Safe Water

During floods and power outages

Drinking Water Safety After a Flood/Power Outage

Emergencies can happen and when they do, the best strategy is to already have a plan in place. This includes knowing the proper water safety precautions to take if floods or prolonged power outages do occur.

If you use water from a private well, a power outage will normally cause the water pump to fail. In this situation, you should always use another source of safe water, such as commercially bottled water or follow the instructions below to temporarily treat your water. If you have a back-up generator, you may continue to use the water as you did before the power failure.

If you have a private treatment system for your drinking water such as ultraviolet light, make sure the treatment system is running properly once the power is restored. Before drinking the water, flush all lines by letting the water run for two minutes. The safety of your water should be confirmed before use.

Most municipal water treatment plants have backup generator systems in place and the water systems are still reliable, however, you should listen to local emergency officials in the event that other precautions or water conservation messages are put in place.

Follow these methods to keep your water safe during and after flood conditions or prolonged power outages:

  • If available, use bottled water that has not been exposed to flood waters.
  • Boil water for one minute to make it safe. Boiling water will kill most types of disease-causing organisms that may be present.
  • If the water is cloudy, filter it through clean cloths or allow it to settle and then draw off the clear water for boiling.
  • If you can't boil your water, disinfect it using household bleach. Bleach will kill some, but not all, types of disease-causing organisms that may be in the water.
  • Add 1/8 teaspoon (or eight drops) of regular, unscented liquid household bleach per four litres of water. Stir it well and let it stand for at least 30 minutes before you use it.
  • Store disinfected water in clean containers with covers.
  • If you have a well that has been flooded, the water should be tested and disinfected after flood waters have receded.


Safe drinking water should always be used for the following:

  • Making ice; juice, coffee, tea and infant formula - Note: Ready-to-serve infant formula is the safest option for formula-fed babies if water safety is a concern
  • For cooking and washing fruits and vegetables
  • Washing hands and brushing teeth
  • Dish washing - for extra safety, pour a capful of bleach into a sink full of clear water for rinsing dishes.

Source: U.S. Food and Drug Administration, What Consumers Need to Know About Food and Water Safety During Hurricanes, Power Outages and Floods - June 2018

External Links

Well Disinfection Tool - Public Health Ontario

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