Wed. Nov 29th, 2023
Field Basics: Drinking Water

Whitney Arnott is a hiking and canoeing enthusiast who likes to spend days at a time in the backcountry when she’s not working at the Ontario Parks branch.

Here are her tips for having safe drinking water when you’re out in nature.

When it comes to drinking water in the backcountry, you may think it will be easy. There is a lot of water around you, right?

While that’s true, it’s not as simple as turning on a faucet at home or submerging the bottle below the surface of the water to fill it.

Untreated water found in lakes, rivers, ponds, etc. It is not safe to drink. It can contain waterborne parasites and diseases like giardiasis (also known as beaver fever) or E. coli, which can make you sick.

Woman drinking water on a trail.

To reduce your risk, follow these steps to get clean, drinking water:

The basic rules

It is important to treat ALL water you drink in the backcountry, even if it “looks” clean or if you see wildlife drinking from it.

Always get untreated water from moving water. Stagnant or stagnant water sources are more likely to contain harmful microorganisms along with algae and mud, making them difficult to clean.

When collecting raw water, be sure to use a different container than the one you use to drink from. You don’t want raw water to contaminate the spout of your drink (i.e. the rim of your water bottle).

Remember to properly treat water used for drinking, preparing baby food or formula, brushing teeth, or washing dishes.

Don’t give up water because the treatment creates an extra step. Long, hot days and prolonged exercise mean your body will need more hydration.

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Gravity water filter in the field.

Choose your filtration method

Boil | Tablets and Drops | Filters | Ultraviolet light

Depending on the length of your trip and your personal preferences, your water filtration method may vary. As with all options, follow the manufacturer’s instructions for proper use.

Whitney’s pro tip: I carry at least two water filtration methods on my travels so I don’t get stuck without clean water. Choosing my filtration methods carefully also works in my favor because some of them work better when combined.


Boiling water. Most experts recommend boiling water as the first option, as it is the only method guaranteed to eliminate ALL pathogens when done correctly.

Just keep in mind that even if you cook food in boiling water, it will need to be boiled beforehand, which increases cooking time.

Whitney’s pro tip: I boil the water for five minutes. The time can vary depending on variables like fuel and altitude, so I always make sure it’s boiling for at least five minutes before cooking it or letting it cool to drink.

Chlorine tablets and iodine drops (disinfection)

When there is fuel reserve or when you need water while traveling, iodine tablets and drops are an ideal alternative.

Follow the manufacturer’s instructions for how much to use compared to the amount of water you are treating, then wait the indicated period before consuming.

Whichever method you choose, make sure they are sealed properly and stored in a waterproof bag, so they remain intact for use.

Important: Iodine-disinfected water is NOT recommended for pregnant women, people with thyroid problems, people with known hypersensitivity to iodine, or continuous use for more than a few weeks at a time.

Whitney’s Pro Tip: I carry these options with me so I can refill my water bottle or hydration pack throughout the day without having to take extra gear out of my pack.

Water filtration methods for the field.


There are a few different filtering systems available, such as:

  • straws that are placed directly in the water and drunk
  • Bags that can filter a couple of liters at a time using gravity.
  • Pumps through which you push water using your own force.
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No matter which you choose, try to collect water that is as clean as possible as leaves, algae, mud, etc., can clog the filter.

Different filters treat different pathogens, so it’s important to talk to your local outdoor products dealer for advice specific to your use and needs. An “absolute” filter (NSF 53 or 58) with “cyst removal” on the label should be chosen to achieve the most effective cyst reduction.

Plan accordingly because some filter bags allow you to filter a decent amount of water, but they can take a while to work. They also require special storage methods that do not compromise the filter; Follow the manufacturer’s instructions for storage and maintenance.

Disinfection and filtration alone may not remove all pathogens; however, if used in combination, they will provide more effective pathogen removal.

Whitney Pro Tip: This is a great option when I want to save fuel (for multi-day trips) but have time to filter the water once I’m set up at camp. Between tablets and a gravity filter, I can usually meet all my water needs and still have a backup option if something fails.

ultraviolet lights

UV lights are a lightweight solution that works quickly and are a great on-the-go option. Some require batteries, so carrying more is essential.

As these units can only operate with low turbidity water, it is important to always pre-filter the water before using the light.

Man drinking filtered water while camping.

Clean water is the priority

There are a large number of water purification methods that can provide you with clean, drinkable water in the field.

The most important thing is that you have one that suits you and your type of trip, and that you always carry a backup method.