Every household should have an emergency water supply for everyone in their home. Three gallons per person should be enough to cover 3 days. Keep an extra gallon or two for your pets too. It’s okay to store water in plastic soda bottles as long as you sterilized them with a little household bleach (no more than 8 drops per gallon should do it). It’s important to store them in a cool, dark place. Be sure to label each one with the date, and replace every 6 months (you can use the old water in your garden or for other household uses.
In the event of a natural disaster, you will be glad you did this!
Note: The Earthquake Supply Center in San Rafael has larger water storage bins that keep water safe for drinking for up to 5 years. Also, Goodman Building Supply in Mill Valley has a good selection of emergency supplies.