Boiling is the most reliable method to make water safe to drink. Bring water to a vigorous boil, and then allow it to cool; do not add ice. At high altitudes, allow water to boil vigorously for a few minutes or use chemical disinfectants. Adding a pinch of salt or pouring water from one container to another will improve the taste.

As a last resort, water that is uncomfortably hot to touch can be made safe for drinking and for brushing teeth after it is allowed to cool. However, many disease-causing organisms can survive the usual temperature reached by the hot water in overseas hotels.