During an emergency, the drinking water source should be:

During an emergency, the drinking water source is assumed to be unsafe primarily because emergencies can lead to contamination from various sources such as flooding, disruptions in water treatment processes, or damage to infrastructure. These situations can introduce pathogens, chemicals, or other hazardous materials into the water supply, compromising its safety.

When a drinking water source is assumed to be unsafe, it guides appropriate responses, including the need for water purification, boiling, or using bottled water until the safety of the water can be verified through testing. This approach helps protect public health by ensuring that individuals are not consuming potentially contaminated water, which could lead to illness or further complications in already vulnerable situations. Given the uncertain conditions during an emergency, erring on the side of caution is crucial.