Water purification in winter presents a different set of problems than during the warm weather in which we normally camp. If we have to bug out or depend on our preps, we should be prepared for it to occur during the worst time of the year. As I watch the nasty weather in so much of the country, I figured this would be a good time to discuss the subject.
Remember that water from streams or other outdoor sources in the wintertime may have the same bacteriological or other contaminants as summer. Many of the water purification devices that we depend on during the summer will not work the same during cold weather.
Chemicals are a good example; chemical treatments are not as effective at low temperatures. Water to be treated that is colder than 68 degrees F will take longer. On their website Polar Pure a manufacture of iodine crystals makes the following statement in their question and answer section.
“Question: How long should I treat very cold water (35° F for example)?
Polar Equipment uses EPA standards to determine dosage and treatment time. Lower temperature water treatment times have not been determined by EPA for any chemical water disinfectant products at this time. We cannot recommend treatment times for water that is colder than 68° F; we can only recommend treating longer. One suggestion is to warm the water to be treated to 68° F if possible either in a sunny spot or with a camp stove (if backpacking or traveling).
EPA tests used an aqueous solution of iodine like Polar Pure as well as other chemicals and chose a treatment time of 20 minutes. EPA tested only two temperatures — 42° F (5 ° C) and 68° F (20° C). The “kill rate” at the coldest 42° F water was 85% after 20 minutes. The “kill rate” for 68° F was 100% after 20 minutes. EPA did not test the colder water again after the 20 minutes to determine when 100% kill rate was attained.”
Chlorine dioxide tablets like Katadyn Micopur and AquaMira all have problems when used in cold weather.
Here’s an excerpt from an Environmental Protection Agency Report showing that Chlorine dioxide’s effectiveness in killing cryptosporidium (cysts) decreases in cold water. “In a study, LeChevallier et al. (1997) found that reducing the temperature from 68°F to 50°F reduced the disinfection effectiveness of chlorine dioxide on Cryptosporidium by 40 percent, which is similar to previous results for Giardia and viruses.
One suggestion to help you use chemicals for water purification is, heat your water to body temperature or higher, pour it into a water bottle, and add one chlorine dioxide tablet for each quart of water. Then use the hot water bottles in your sleeping bag at night to stay warm, because the bottles stay insulated this lets the chlorine dioxide work. The published guidelines for chlorine dioxide tables show that they require 60° F or hotter water to work. They require 15 minutes to kill protozoa and bacteria, and 4 hours to kill cryptosporidium cysts.
If you have to melt snow for water, if ice is available, melt it, rather than snow. One cup of ice produces more water than one cup of snow. Ice takes less time to melt.
Using a water filtration pumps such as the PUR, First Need, or the Katadyn is not recommended in subfreezing temperatures. Because the water in filters can freeze preventing them from working and the water may expand and may crack the filter, rendering it inoperable or permitting the transfer of harmful microorganisms. For these reasons, filters should be used with great caution in the winter.
One way to prevent your water filter from freezing up is to put it in a plastic Ziploc bag and sleep with it in your sleeping bag. The plastic bag is to prevent any water trapped in your filter from leaking into your sleeping bag.
Battery operated devices like the SteriPEN can be unreliable because they rely on batteries which lose energy much faster in cold weather.
Boiling water still works for water purification, while as I have mentioned in other posts water pasteurizes at 160° F, unless you have a good thermometer with you I would bring the water to a full boil to be on the safe side.
As you can see from the above information water purification in cold or freezing weather takes a bit more effort than in warm weather. But it is still possible.