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Treat Water

Did you know that there is a 63% chance of a major earthquake occurring in the Bay Area within the next 30 years? After such an event, your water supply might be unavailable for up to 72 hours or more.

If you run out of stored drinking water, don’t worry: you can treat water from certain sources in your 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 your home are appropriate for drinking.

Which Sources of Water Can You Drink?

Sources of water you CAN treat and drink include:

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

Sources of water you CANNOT treat and drink 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 you identify a source of potable water, you can treat it by disinfecting it or boiling on a camping stove.

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
Add 8 drops of bleach per gallon of water
Shake or stir, then let it stand for 30 minutes
For disinfected water, a slight chlorine taste or smell is normal.

Boiling Water

To treat water by boiling it:

  • 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

*Additional Notes on Disinfecting Water

Your 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 Chlorine

Drops per Quart/Gallon of Clean Water 

 Drops per Liter of Clean Water

 Unknown or 1%    

 10 per Quart - 40 per Gallon

 10 per Liter


 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.

How Do I Store Water, Again?

Learn how you can store water.

Last updated: 10/1/2019 1:00:57 PM