Camping Water Purification Time Guide
Find the right treatment time for your backcountry water source based on elevation and purification method.
Covers boiling, UV, and chemical tablets.
Waterborne illness from untreated backcountry water is very real and very unpleasant.
Giardia and Cryptosporidium — the two most common backcountry pathogens — can survive in cold, clear mountain streams that look perfectly safe.
Boiling is the most reliable method and requires no equipment beyond a stove.
The key variable is altitude: water boils at lower temperatures as you go higher because atmospheric pressure decreases.
At sea level, water boils at 100°C (212°F).
At 3000 m (10000 ft), it boils at about 90°C (194°F).
Most pathogens die well before 100°C, but the reduced boiling temperature at altitude means the safety margin shrinks, so longer boil times are required.
CDC and WHO guidelines:
- Below 2000 m (6500 ft): 1 minute of rolling boil
- Above 2000 m: 3 minutes
UV treatment (SteriPen and similar devices) uses ultraviolet light to destroy the DNA of bacteria, viruses, and protozoa.
It works in 60-90 seconds for clear water but becomes ineffective in turbid (cloudy) water because particles block the UV rays.
If the water has suspended sediment, pre-filter through a bandana or coffee filter before using UV.
Chemical tablets (iodine or chlorine) kill bacteria and viruses but work more slowly, especially in cold water.
Cryptosporidium is resistant to iodine and low-dose chlorine — not killed by standard tablet doses.
For comprehensive protection with chemical treatment, choose chlorine dioxide tablets (not iodine or standard chlorine), which are effective against Crypto but require 4 hours of contact time in cold water.