Our tips for filtering and purifying water while hiking

Discover our range of portable water filters

Step 1: Plan your hike and locate water sources

Using maps, GPS apps, or advice from social media, locate as many water points along your route as possible and try to gather the most recent information about their condition. Once on the ground, avoid stagnant water unless it's an emergency and you have an appropriate purification system. Prefer moving water, and try to collect it as high up its source as possible to minimize the risk of contamination from animal carcasses or toxic plants upstream. To fill your container (bottle, water reservoir, etc.), place it in the water in the direction of the current. This will limit the amount of suspended materials (vegetation, dirt, minerals...) in the collected water.

Step 2: Water filtration

Filtration is used specifically to remove suspended particles, thus clarifying the water. However, it does not guarantee that the water is potable because pathogenic microorganisms are not necessarily filtered out or removed by this process. Still, filtering water has several benefits. First, it removes debris, making it more pleasant to drink. Then, if you apply a purification method afterward, such as boiling or UV exposure, pre-filtering prevents clogging of the purification system with sediment, making it easier to maintain and extending its lifespan.

For basic filtration, a simple cloth like a bandana may suffice. However, I prefer using a more advanced device, like the Millbank filtration bag, a robust canvas bag formerly used by British soldiers. You first soak it to absorb water, then fill it, and the water slowly filters through, leaving the sediment behind.

Filtration bag in action

If my water source is rich in sediment, I filter it with this bag before purifying it with one of my filters, either by boiling or chemical treatment.

Step 3: Water purification

This time, the goal is to make the water drinkable without the risk of ingesting anything that could make you sick. The simplest method is to boil the water after filtration, for one minute if you're at sea level and for three minutes if you're at altitude. The second method is chemical purification, using chlorine, iodine, or bleach in the form of drops or tablets. Micropur tablets are one example. They require waiting a certain amount of time before drinking the water (usually about 30 minutes).

The third method of purification is UV treatment. Place a bottle (made from plastic that doesn't retain UV rays) in the sun for 6 to 24 hours, which will neutralize bacteria, viruses, and protozoa if the water is relatively clear (turbidity slows down or even prevents UV rays from working). But this method is slow and dependent on sunlight. The principle of using UV rays has been adapted into technology in the form of the Steripen, an electronic purifier that, when submerged in water and stirred, destroys pathogens in one liter in 90 seconds. Two limitations of this model: if the water is rich in sediment, you'll need to filter it first, and you'll be dependent on its battery.

The rise in demand for water filters by nature enthusiasts has led to the development of numerous technologies by brands. It's now easy to find a product that provides both filtration and purification, like filter bottles, straws, or pumps. In addition to being practical, they are easy to use. These purifiers employ different purification and filtration methods, such as ceramic filters, activated carbon, ion exchange, etc. With a little research, you’ll surely find a model that suits your needs in terms of weight, bulk, ease of use, and performance.

In the past, filtration solutions were designed to neutralize only bacteria, protozoa, and viruses. However, environmental concerns, soil and water pollution, have added quality criteria to different manufacturers, such as the filtration of heavy metals, microparticles, pesticides, and various chemicals. I should point out that filters still have limitations that marketing often overlooks, particularly when it comes to virus filtration. When a filter claims to neutralize "THE viruses," I would prefer if they said "SOME viruses," as completeness in this matter might be presumptuous. But having used various references in filtration and purification (brands like Grayl, Katadyn, MSR, Sawyer, Öko) for years, I’ve never had an issue. Lyophilise & Co offers a variety of what’s available on the market:

• Soft or rigid filter bottles
• Pump filters
• Filter straws
• Tablets
• Expedition jerrycans
• Replacement filters
• Household filters

Note: If you're lost among all these filters, we've put together a buying guide to help you choose the right water filter.

Step 4: Maintaining your water filter

Regardless of the filter you choose, make sure to follow the instructions on maintenance, cleaning, and storage between uses to avoid heading out with a filter that could have developed pathogens over time.

In most cases, it's recommended to clean your filter after each use, dry it properly, and store it in a suitable place.

Thanks to Yves Jean, bushcraft instructor and first responder, for writing this article.

To clarify, manufacturers use the term "water filters" for systems that eliminate bacteria and protozoa. The term "water purifiers" is used to define systems that also eliminate viruses. Lyophilise & Co has opted to keep these terms, different from those explained by Yves Jean in his article, to avoid confusing buyers.

If this article has convinced you to get a filtration system, here are the most popular models among hikers:

• Katadyn BeFree Soft Bottle
• Sawyer Mini Straw
• Öko Bottle