WAT-3.3 Boiling

How long to boil

If you can boil water, boil it. Ready.gov calls boiling "the safest method of treating water".

1. Clear cloudy water first. EPA: "If water is cloudy, let it settle and filter it through a clean cloth, paper towel, or coffee filter." More in WAT-3.2 Clearing cloudy water.
2. Bring it to a rolling boil: the whole surface bubbling hard, not just small bubbles rising from the bottom.
3. Keep it boiling for at least one minute. Start counting when the rolling boil starts, not when the pot goes on the heat.

"Bring water to a rolling boil for at least one minute." (EPA)

In hills and mountains, boil for three minutes: see Altitude below.

What boiling does not do. It kills germs. It does not make water with chemicals in it safe:

"However, boiling or disinfection will not destroy other contaminants, such as heavy metals, salts, and most other chemicals." (EPA)

If the water may hold fuel, chemicals or salt, for example floodwater or seawater, boiling is not enough. Ready.gov notes that "distillation will remove microbes (germs) that resist these methods, as well as heavy metals, salts and most other chemicals." See WAT-3.7 Distillation and WAT-3.8 Choosing a method.

Source: [1] Emergency Disinfection of Drinking Water · [2] Water

Altitude

Water boils at a lower temperature the higher you are, so it needs to boil for longer.

"At altitudes above 5,000 feet (1,000 meters), boil water for three minutes." (EPA)

Review note. EPA's sentence gives two different heights: 5,000 feet is about 1,500 m, not 1,000 m. Until a reviewer settles this, the table uses the lower one, 1,000 m (about 3,300 feet). Two extra minutes of boiling cost little fuel.

Source: [1] Emergency Disinfection of Drinking Water

Fuel cost

No federal source used here gives fuel figures. This section is BlackoutOS planning advice and is marked for review (question WAT-3.3-q04 has no source yet).

• Plan your fuel for the times above: one minute at a rolling boil, three minutes in the hills and mountains.
• Boil drinking and cooking water first. That is the water that must be safe.
• Put a lid on the pot. Covered water comes to the boil sooner, on less fuel.
• Boil one full pot rather than several small ones, then store it as described below.

Burning fuel makes carbon monoxide. Ready.gov:

"Generators, camp stoves or charcoal grills should always be used outdoors and at least 20 feet away from windows."

"Do not use a gas stove or oven to heat your home. It increases your risk of carbon monoxide poisoning."

"Carbon monoxide is a colorless, odorless gas that can kill you, your family and pets."

20 feet is about 6 m.

Source: [3] Power Outages

Cooling and storing

"Let water cool naturally and store it in clean containers with covers." (EPA)

• Use clean containers with lids. For long-term storage, Ready.gov advises to "purchase food-grade water storage containers".
• Pour from the container; do not dip cups or hands into it. More in WAT-4.4 Keeping clean water clean.
• How long stored water keeps, and labelling: WAT-1.3 Storing and rotating.

Flat taste. Boiled water tastes flat. It is still safe.

"To improve the flat taste of boiled water, add one pinch of salt to each quart or liter of water, or pour the water from one clean container to another several times." (EPA)

Ready.gov explains why pouring works: "Boiled water will taste better if you put oxygen back into it by pouring the water back and forth between two clean containers."

Source: [1] Emergency Disinfection of Drinking Water · [2] Water