What to Know During a Drinking Water Emergency 


In times of unexpected drinking water emergencies, the California Governor’s Office of Emergency Services (Cal OES) encourages everyone to be well-informed to safeguard the health of yourself and your loved ones. 

Understanding Unsafe Water Notices 

Unsafe Water Notices are critical tools used to communicate potential risks associated with water contamination. These notices are issued by water service providers or local governments in response to varying degrees of water contamination: 

  • Boil Water Notice: A Boil Water Notice is issued when the water supply is compromised by microbiological contamination that can be neutralized through boiling. The recommended method is to bring the water to a rolling boil for at least one minute which effectively eliminates most disease-causing microorganisms. If you are unable to boil the water, find alternative sanitation methods from the California Department of Public Health (CDPH). 
  • Do Not Drink Notice: When the water supply is deemed unsafe due to a contaminant that cannot be removed through boiling or disinfection, a Do Not Drink Notice is issued. In such cases, it’s important to find an alternate source of water for drinking, food preparation and brushing teeth. While the contaminant may not pose a threat through bodily contact, it’s recommended to avoid using this water for activities involving consumption or oral contact. 
  • Do Not Use Notice: A Do Not Use Notice is employed when a water supply is considered unsafe due to suspected or unknown contamination, or when a known contaminant poses a health risk through bodily contact. In these situations, it’s advised to seek an alternative water source for all purposes, including drinking, food preparation, brushing teeth, personal hygiene and other household tasks. This notice may also be issued as a precautionary measure when the quality of water is uncertain. 

Unsafe Water Notices will help you make informed decisions and take the necessary precautions during drinking water emergencies. For more detailed guidance and information, you can refer to CDPH’s Safe Drinking Water Guide. 

Determine Water Needs 

Clean drinking water may not be available following a disaster. Your regular water source could be cut off, compromised or contaminated. Prepare yourself by building a supply of water that will meet your family’s needs during an emergency. View the recommended emergency supplies list. 

Store at least one gallon of water per person per day for several days, for drinking and sanitation. A normally active person needs about three-quarters of a gallon of fluid daily, from water and other beverages. However, individual needs vary depending on age, health, physical condition, activity, diet and climate. 

Take the following into account: 

  • Children, nursing mothers and sick people may need more water. 
  • A medical emergency might require additional water. 
  • If you live in a warm weather climate more water may be necessary. In very hot temperatures, water needs can double.