Guide: How to Choose Your Water Filter?

Why having a water filter ?

Before helping you choose, let’s try to convince those who are still unsure about purchasing a water filter. If you're already convinced, feel free to move on to the next section.

During dynamic outdoor activities (hiking, mountaineering...), it’s recommended to drink at least one or two sips every 10 minutes. This helps avoid dehydration. Over the course of a day, this amounts to a large quantity of water. A water filter’s purpose is to reduce the weight of your backpack because you can refill your bottle as you go, whenever you come across a water source.

This requires planning your route and identifying the water points you will pass. It could be a stream, river, spring, fountain, or even a puddle. Some filters can even handle turbid water, provided it’s not stagnant. The puddle must be recent. The water filter provides comfort. It’s relatively compact and lightweight (depending on the model), allowing you to not worry about the amount of water you need to carry during your outdoor activity.

For stationary activities (camping, base camps, humanitarian work...), the principle is the same. Planning for the necessary water supply over several days or for multiple people can often be a headache. A water filter improves your living conditions. The question of water is no longer a problem because you can easily refill your supply at the nearest water point.

As you can see, each filter is designed to meet a specific need. While they all have the same goal — making water potable — their ergonomics differ. Each model has its own advantages and disadvantages.

Characteristics of a Water Filter

Now that you understand the importance of having a water filter for any outdoor activity, let’s look at its key characteristics.

The Technology The technology in water filters is often misunderstood or poorly explained, but it’s actually quite simple. Each filter uses a technology, which is a component that will filter the water. Here are the different technologies found in water filters:

• Membrane: A perforated part of the filter that allows pressurized water to pass through. Some fiber membranes, like those of the Sawyer filter, are self-cleaning and have an extremely long lifespan. Depending on the model, filtration removes most impurities (up to 99.999%).
• Fiberglass: Aside from viruses, this system captures most impurities, including chemicals. Pumping is easier with this technology, but it cannot be cleaned. Fiberglass filters typically have a shorter lifespan compared to membrane filters. Katadyn uses this technology.
• Hollow Fibers: Almost equivalent to fiberglass, hollow fibers don’t capture chemicals or improve the taste of water. However, they are compact and lightweight, ideal for those looking for an ultra-light filter.
• Activated Carbon: This is a very basic technology effective at filtering chemicals and improving the taste of water. Activated carbon filters are not effective at filtering protozoa, bacteria, or viruses.
• Ceramic: Although it is ineffective against viruses, the ceramic filter is one of the most effective on the market. It is suitable for all types of water, including very turbid water. It is also easy to clean. The only downside is its fragility — if the filter is dropped, the ceramic cartridge can break, making it unusable.

There are also UV treatment systems (like Steripen water purifiers), ion exchange systems, and, of course, chemical treatments (which are almost the only ones effective against viruses).

Performance in Microns

The technologies listed above allow for the filtration of pathogens of various sizes. The more effective the filter, the smaller the micron size of the pathogens it can filter. Here are some examples of filters available on the market:

• Sawyer Mini: It uses fiber technology with a 0.1 µm rating. One of the most efficient filters, it features a membrane filter.
• MSR Guardian: It can stop viruses with a filtration size of 0.02 µm. The Guardian is one of the most comprehensive filters on the market.
• Lifestraw and Katadyn filters (hollow fibers) are around 0.2 µm, which is also the case for the MSR TrailShot.
• Aquamira Frontier Pro: It has a 2 µm filter and is much less effective.

For reference, here are the sizes of common pathogens:

• 1µ to 15µ: Amoebic dysentery, giardia, lamblias, cryptosporidium, etc.
• 0.2µ to 5µ: E-coli, salmonella, cholera, etc.
• 0.02µ to 0.2µ: Hepatitis A, Norwalk virus, rotavirus, polio virus, etc.

Depending on your activity, the micron performance might be more or less important. If you're hiking in Europe or North America, filters around 0.2 µm will suffice. However, for travel in developing countries, it’s better to choose a filter with strong micron performance to avoid contamination risks.

Flow rate

On average, a portable filtration system has a flow rate between 1 and 2.5 liters per minute. This means it takes little time to fill a bottle, which is ideal for hiking or self-sufficiency races. Time-saving and efficient!

Filters for stationary activities (bushcraft, bivouac, etc.) usually have a lower flow rate. These include gravity filters, which have other advantages. Most require no effort, as the water flows by itself. So, pay attention to this feature when choosing your water filter, and choose one with an appropriate flow rate: high if you're in a rush or without a specific flow rate if you’re not in a hurry.

Autonomy

The autonomy of filters varies greatly. Some allow you to purify 100 liters of water, while the most autonomous filters can purify hundreds of thousands of liters. For the less autonomous filters, it’s important to note that most allow you to buy replacement cartridges. The water filter is not disposable.

In any case, a water filter needs to be maintained. If not, its autonomy will decrease significantly due to bacteria, protozoa, and other pathogens that will clog the filter element.

Also, some products are not suitable for muddy or turbid waters. Ignoring the manufacturer’s recommendations can result in clogging the filter and making it ineffective. Autonomy is important when choosing your filter, but make sure to follow the usage and maintenance conditions to achieve the specified values.

Weight size ratio

Enfin, le poids et les dimensions sont des critères à prendre en compte pour toute activité nomade, du bushcraft au trekking en passant par les road-trips en van. Au même titre qu’une tente ou qu’un réchaud, plus votre modèle est compact et léger, plus cela est confortable. Il se transporte et se range facilement.

En revanche, certains filtres ultra légers ne sont pas adaptés pour des groupes ou pour un besoin d’eau élevé. Il convient donc à chacun de faire le choix le plus pertinent selon sa situation et ses besoins.

Different Types of Water Filters

Each water filter has the characteristics mentioned earlier, but they can still be segmented by type. Each type of filter is better suited for a specific activity. You can therefore choose the filter most suited to your situation and compare the different types based on their characteristics.

The Filter Straw

The filter straw is a tube through which you suck. The water, passing through the filter, becomes drinkable. The advantage of this filtration system is definitely its weight and size. The filter straw is lightweight and compact, making it easy to slip into a backpack. It’s perfect for ultra-light hikers (MUL).

Additionally, depending on the model, some straws can be attached to a bottle, water pouch, or container. This is the case for the Sawyer Mini filter. This versatility is appreciated by many users. You can:

• Drink directly from the water source
• Fill your bottle and drink through the straw (1)
• Attach to a bottle or water pouch and transfer the water to a bottle (2)
• Attach to a water pouch (3)

The Filter Bottle

Very similar to filter straws, the filtered water bottle works the same way. You simply suck to obtain filtered water. Its main advantage is the comfort it provides. All you need to do is fill your bottle as you pass by water points (streams, fountains...) and drink like with a regular bottle. No need to screw, transfer, etc.

The most well-known model is certainly the LifeStraw Go 2 filter bottle. Equipped with an activated carbon cartridge in addition to the hollow fiber filter, it makes the bottle effective against bacteria, protozoa, and chemicals. It also helps reduce bad tastes, something the filter straw doesn’t do (you would then need to use a Micropur tablet, which we will discuss later).

As for the most common model in hiking, it is the Katadyn BeFree. Unlike the LifeStraw Go 2, the BeFree does not have an activated carbon capsule. However, its flexible bottle allows it to take up less space in your backpack.

Regarding the disadvantages of filtered water bottles, they share those of the filter straws. They are not recommended for filtering turbid water. This is because most water bottles have a hollow fiber or membrane filtration system. Additionally, a filtered water bottle can be more bulky and heavier than a filter straw, as we saw with the LifeStraw Go 2. For these reasons, some prefer to choose a straw and filter water directly into their unbreakable Nalgene bottle.

The Pump Water Filter

As the name suggests, you need to pump to filter the water. No more sucking; it’s more manual work. You’ve got it, this type of filter is especially suitable for groups. To filter the water, you need to place the hose in the dirty water and pump above a reservoir (bottle, water pouch, jerrycan…). With a flow rate of one liter per minute for the less advanced models, it can require quite a bit of effort depending on the desired amount.

But the major advantage of the pump water filter is its ability to purify turbid water. It allows you to eliminate all contaminants: bacteria, protozoa, and even viruses in some models. We’re thinking of the Guardian made by the brand MSR. Unlike most pumps with ceramic filtration, the Guardian is made with hollow fibers. The increased volume of these fibers makes it effective against microorganisms as small as 0.02 microns (compared to 0.2 microns for other hollow fiber filters), which is the size of a virus. In short, this is what makes it one of the most efficient models on the market.

Gravity Water Filter

Gravity filtration meets a different need: having large quantities of drinkable water. Gravity filters work without pumping or sucking. They require no effort. Simply fill the reservoir, then open the tap, and potable water will flow out (much like jerrycans, really). This proves to be very practical for camping, base camps, or bivouacs. It’s also very popular with groups.

As for the downsides, this varies depending on the model. Gravity water filters like the LifeStraw Mission and MSR Guardian Gravity filter viruses (hollow fibers with 0.02-micron pores) but have a very low flow rate (between 20 and 50 cl per minute). The BeFree Gravity has a better flow rate with 2 liters per minute but does not filter viruses.

Finally, there are gravity filters designed for more stationary uses. Think van lifers, RVs, or forest cabins. The most famous ones are from the Berkey range. While the price may deter some, there are less expensive and just as effective alternatives.

These include Gravidyn and Ceradyn filters designed by the world leader in water filtration, the Swiss brand Katadyn. The operating principle is simple: you fill a first reservoir with non-potable water. This water passes through ceramic filters and flows into a second reservoir. The flow rate is slow (4 liters per hour), but once filtered, you can open the tap to serve yourself, like a wine box. The flow rate is then fast. Requiring no effort, you can filter the water while you hike or sleep.

To summarize, gravity filtration is usually slower and more cumbersome to set up, but it requires no effort.

Chemical Water Filter

Finally, there are chemical water filters. Forget all the characteristics mentioned earlier: flow rate, technology... This is a somewhat different filtration system. Available in liquid, powder, or tablet form, you simply add it to your water to disinfect and purify it.

While they don’t work well in turbid water, they are very effective in clear water. Chemical treatments like Micropur, which contain chlorine and silver, eliminate viruses, bacteria, and protozoa. Micropur is very useful as a complement to a filter when you have slight doubts about the water or to preserve your water. For example, if you have a 10-liter water jug, one Micropur Classic tablet can preserve it for up to 6 months.

Very light and compact, this chemical filtration system allows you to eliminate any risks when drinking questionable water. For this reason, it’s used in all fields: navigation, bushcraft, hiking, travel...

Choosing the Right Water Filter for Your Activity

Now that you have all the information to choose the ideal filter, let’s look at the most suitable filters for a few outdoor activities.

Which Water Filter to Choose for a Trek like the GR20?

During a hike, your main enemy is weight and space. You need to make sure you only carry the essentials. Otherwise, you risk tiring out quickly and even causing back pain with heavy loads. Moreover, you need to hydrate frequently and quickly. So you need a water filter within easy reach.

✅ The top choice: Microfilters are often sufficient. Therefore, a straw or a bottle will do the trick, as long as you have access to clear water. Also, bring Micropur tablets as a backup.

Models: Sawyer Mini, Katadyn BeFree, LifeStraw Go 2
Alternative: If you’re in a group or hiking in risky areas, opt for a more powerful filter. The pump filter is ideal for its ability to filter muddy water.

⛔ Avoid: Gravity filters are too bulky and take too long to set up.

What Filtration System to Choose for a Van or at Home?

When you have a base, the weight and size of the filter are less important. Choose a filter suited for multiple people and with a reservoir to store the water.

✅ The top choice: Gravity filters are great because they require no effort. If possible, choose a model that filters water even when you’re not at home.

Models: British Berkefeld
Alternative: A water bottle may be an option because it’s very easy to use. But its small capacity is a drawback since you’ll need to constantly refill it.

⛔ Avoid: Filter straws require sucking and are not recommended for group use.

Choosing the Right Water Filter for Traveling

We’re talking to tourists now. For example, you’re planning to visit Peru: Machu Picchu, the Ica Desert, Lima... It’s not complicated to find a place to stay for the night, whether with locals, in a hostel, or a hotel. However, be cautious with tap water. It’s very rarely potable.

✅ The top choice: A filtered water bottle is ideal because it’s easy to carry and refill. If you equip it with a carabiner (some models come with it), you can attach it to your backpack.

Models: Katadyn BeFree

Alternative: In some countries, access to potable water is very difficult, and the only available water points are dirty or even muddy. A pump filter can therefore be very useful. Make sure to research the water access conditions in the country you’re visiting.

⛔ Avoid: Gravity filters are not suitable for nomadic travel for the same reasons mentioned earlier: they’re heavier, bulkier, and more restrictive.

The Perfect Water Filter for Bushcraft or Survival

Bushcraft involves living as autonomously as possible in nature, with minimal impact on the environment. It differs slightly from survival, which, as the name implies, is about surviving in a hostile environment. However, both terms share the concept of autonomy — autonomy for sleeping, feeding, and also hydrating.

✅ The top choice: For bushcraft, an outdoor activity for pleasure, a microfilter is sufficient. For survival, you must consider the worst-case scenario (contamination, turbid water...). A pump filter is therefore necessary, with the ability to also eliminate viruses if needed.