Boiling is the oldest and most basic way to purify water. A rolling boil will destroy any pathogens. You can kill microorganisms at sustained heat that is less than a boil, but it’s difficult to measure in the field. Make sure the water is actually boiling. A rolling boil is big bubbles that shake the pan, not a few tiny bubbles on the bottom of the pan. To be safe, bring the water to a rolling boil for 3 to 5 minutes. As a general rule, add one minute of boiling time for each 1,000 feet of elevation above sea level. If you’re using the water for cooking, there’s no extra time, fuel weight, or cost involved. But boiling water for drinking is slow and tedious, and adds to the weight of the fuel in your pack. The real weight of boiling water is the weight of the extra fuel you need to carry.Interview the caregiver first. This will cost you money, but you will be able to determine if the fit is good or not. Do not be afraid to say no if you do not think the person is appropriate.