How to Safely Store and Treat Water for Emergencies

March 22 marks 63rd anniversary of the 1957 San Francisco earthquake, also known as the Daly City earthquake of 1957. The 5.7 magnitude quake occurred in the Peninsula right off the San Andreas Fault. Luckily, the earthquake yielded minimal damage.

There is a 63% chance of a major earthquake occurring in the Bay Area within the next 30 years. After such an event, the Bay Area’s water supply might be unavailable for up to 72 hours or more. As the anniversary draws near, the SFPUC reminds residents the importance of being prepared for whenever disaster may strike. One of the most important things the agency recommends is to store enough water as part of an emergency kit.

Storing water in case of emergencies.

One Gallon Per Person Per Day: Each family member needs one gallon of water per day. Three gallons per person is enough drinking water for three days, and it is also sufficient for limited cooking and personal hygiene use. Don’t forget pets and family members of all ages. They also need up to one gallon of water per day.

Storing Tap Water: Tap water can be stored without any treatment. Use food-grade plastic containers, such as clean two liter soft drink bottles. Heavy-duty water containers are available at local sporting goods store. Store tap water in a cool, dark place, such as under a sink or in the basement. Label the containers with the date of storage and replace every six months. Stored tap water does not need to be treated before drinking.

Storing Bottled Water: It is not recommended to store bottled water after the seal has been broken. Store bottled water in a cool, dark place and in the original sealed containers. If the bottles are not marked with an expiration date, label them with the date of purchase and replace every six months. Stored bottled water does not need to be treated before drinking.

Water Conservation Tip: An emergency water supply, whether it is tap or bottled, has to be replaced every six months. But instead of throwing the old water away, reuse it to irrigate plants.

But what happens if stored water is out? If stored drinking water is depleted, one can treat water from certain sources in the home. According to SFPUC Supervising Biologist Paul McGregor, “You don’t need a fancy lab to treat your water. In fact, you can do it in your own kitchen.” But keep in mind that not all sources of water in the home are appropriate for drinking.

Gallon water food grade containers to store water for emergencies.

Other Sources of Drinking Water

Sources of water that can be treated for drinking include:

  • Water from the water heater
  • Water from the toilet reservoir tank
  • Water from the coffee maker reservoir

Sources of water that cannot be treated for drinking include:

  • Pool water
  • Spa water

Swimming pool and spa water are not appropriate for drinking, but can be used for flushing toilets or washing. Once a source of drinking water is identified, it can treat by disinfecting or boiling on a camping stove.

Boiling Water

Bring a pot full of water to a rolling boil. Maintain that boil for 3 to 5 minutes in order to kill off bacteria. After the water cools, put it in a sealed container and shake it – this shaking will add oxygen back to the water and improve its taste.

Storing water and labeling date when container was filled.

Disinfecting Water*

To treat water by disinfecting it, use regular household bleach (typically 5.25% sodium hypochlorite), not the “scented”, “ultra” or “color safe” kind. Then add 8 drops of bleach per gallon of water. Shake or stir, and then let it stand for 30 minutes. For disinfected water, a slight chlorine taste or smell is normal.

Bleach may not be 5.25% chlorine, or the percentage may be unlisted. Use the information in the following table as a guide. (Remember, 1/8 teaspoon and 8 drops are about the same quantity.)

 Available ChlorineDrops per Quart/Gallon of Clean Water  Drops per Liter of Clean Water
 Unknown or 1%     10 per Quart – 40 per Gallon 10 per Liter
 4-6%         2 per Quart – 8 per Gallon
(1/8 teaspoon)
 2 per Liter
 7 – 10% 1 per Quart – 4 per Gallon 1 per Liter

Double the amount of chlorine for cloudy, murky or colored water or water that is extremely cold.

After disinfection, the water should have a slight chlorine odor. If not, repeat the dosage and allow the water to stand for an additional 15 minutes.

If the treated water has too strong a chlorine taste, allow the water to stand exposed to the air for a few hours, or pour it from one clean container to another several times.