Crystal clear mountain streams are tempting for a drink, but even in remote areas there are likely pathogens lurking. To avoid severe illness, there are many methods to treat water.

What is treatable?

Not treatable: Chemicals, pesticides, mine run-offs
Treatable: Biological microorganisms

What are we treating for?

Protozoa

Commonly: Giardia, Cryptosporidium
Size in microns: 5 or larger
Caught by: Water filter (1.0–4.0)

Bacteria

Commonly: E. coli, Cholera, Salmonella
Size in microns: 0.2–0.5
Caught by: Microfilter (0.2–1.0)

Viruses

Commonly: Hepatitis A, Rotavirus, Norwalk virus (Concern more in developing countries)
Size in microns: 0.004
Caught by: Water purifier (to 0.004)

(For reference: a hair = approx. 600 microns)

Boiling

Kills everything!

Rolling boil: At least 1 minute
Longer at altitude: Since water boils at a lower temperature
Plan for enough fuel!

Filters

Squeeze bottle, gravity-fed, pump… Whatever style you choose, read the label to know what it filters out.

Most last up to 1000 L & back flush to clean.
Caution in cold: Filters will freeze.

Chemicals

Tablets, tinctures, two-part drops! Read package directions carefully. Sits for at least 30 minutes.

Less effective the colder the water! Example: In 10°C water, only 98% of Giardia is killed at 30 min. Warm water in the sun first to make more effective.

Add juice crystals after wait time to help taste.

Iodine

Avoid if you have allergies, are women over 50, pregnant, or have thyroid issues—consult a doctor first! Won’t kill Cryptosporidium.

Chlorine

Less effective on Giardia. Won’t kill Cryptosporidium.
Household bleach is cheap! 4–6% sodium hypochlorite: 2 drops/L water

(TIP: For murky water, pre-filter with a buff or bandana!)

UV Light

Kills everything!
Speed: Less than 1 minute but only 0.4 L at a time.
Issues: Discoloured water & particulates block light, preventing purification.
Relies on battery & electronics.