8 Ways on how to Filter and Purify Water Outdoors
Discover the most effective ways to filter and purify water outdoors, from classic boiling methods to high-tech UV purifiers and compact filters for every adventure.
In SHORT…
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What’s the best way to filter water outdoors? Learn how different methods—like boiling, filtration, and chemical treatments—remove bacteria, viruses, and sediment from natural water sources.
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How do you choose the right water purification method? Compare the pros, cons, and ideal uses of UV purifiers, squeeze filters, gravity systems, and more to suit hiking, backpacking, or emergency use.
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When should you use purification vs filtration? Understand when virus protection is essential and why combining methods may be the safest choice for challenging environments.
Water is one of the heaviest items you’ll carry whilst outdoors. Every litre adds a kilogram, and if you’re heading out for a few days that’s a fair bit of weight. Luckily, there’s a solution to carrying the kitchen sink on your back and that is drinking water that you might find naturally along your route. This presents its own issue, though, in the sense that most water isn’t safe to drink right from the source; at least if you’re human. Here are some clues on how to filter water outdoors.
How to Filter Water Outdoors: Boiling
This is the cheapest and arguably simplest option if you already own a stove. Simply boil the water and all bacteria & viruses present will be killed; job done. Time is the main issue here. It’ll take five to ten minutes to boil and probably the same again to cool down depending on the time of year. You’ll also need to ensure it’s not full of soil, stones and other debris as obviously boiling isn’t going to filter out visible objects. A solution to this is to use a tea towel or old t-shirt as a makeshift strainer to remove the sediment.
Positives: Cheap & simple
Negatives: Slow, requires fairly clear water if not straining
Bacteria: Yes
Viruses: Yes
How to Filter Water Outdoors: Filtering
A water filter is a quick and safe way to filter water. It is one of the most widely-used methods on this list. Most will filter a litre of water in a minute or so and are relatively inexpensive to maintain. MSR’s TrailShot has become one of our bestsellers thanks to its straw-like functionality which allows you to drink straight from the source. The filter will need replacing, but not until you’ve drank 2000L of water. Let’s be honest, is going to take you a while. It’s worth noting that although filters will eliminate bacteria, they won’t all remove viruses. You’ll have to add chemicals afterwards if you’re in a particularly nasty area.
Positives: Quick, hassle-free
Negatives: Won’t all filter viruses, higher initial cost
Bacteria: Yes
Viruses: No, unless using chemicals after
Purifying
Think of this as a filtration system for regions where water treatment and sanitation aren’t as sophisticated, or where you’re likely to find some form of nasty human-derived viruses such as Hepatitis or Norovirus—we’ve got two options here.
MSR’s Guardian will remove sediment, viruses and bacteria from water sources and was originally designed for the military. You can be sure it’ll work no matter where you are. The downside of this particular purifier is that it’s expensive and bulky, but needs must ey. Taste is vastly improved with the Guardian over a basic filter. It’ll provide some level of protection against heavy metals too. In terms of ease of use, it’s simply a matter of popping the one end in your water source and using the handle to pump water through until clean water emerges from the other end.
Positives: Removes bacteria, viruses, and sediment in bulk. Improves taste.
Negatives: Expensive, bulky
Bacteria: Yes
Viruses: Yes
The other option is a Grayl filter—we stock both the GeoPress and UltraPress. The GeoPress, for example, will remove sediment, viruses and bacteria from around 700ml of water in 8 seconds. They improve taste, just like the Guardian above, and will remove chemicals, heavy metals and microplastics. To filter and purify, fill the inner vessel with water, put the outer over the top and press down—easy. The downside of this option is that you’re limited to the size of the vessel itself. You can only filter 700ml or so at a time. Ideal if you’re by yourself, but if you’re in a larger group or need more water then the Guardian is probably for you.
Positives: Removes bacteria, viruses, sediment, heavy metals, chemicals and microplastics. Improves taste.
Negatives: Limited to vessel size
Bacteria: Yes
Viruses: Yes
How to Filter Water Outdoors: Chemicals
If you don’t own a stove and fancy saving a few quid at the expense of the taste of the water, this is the option for you. Generally you’ll find these chemicals in tablet or droplet form and can be added to your bottle to eliminate both bacteria and viruses.
The positive? They’re incredibly cheap (less than a pub lunch for a box full of the things), effective against bacteria and viruses and take up very little space in your pack.
The negative is that the water should be as clear as possible before treatment, as debris will limit the efficacy of the product. You can strain the water through a tea towel, old t-shirt or similar if you’re really stuck. Another downside is that, in most cases, your water will taste like chlorine after which isn’t pleasant. Lifeventure’s Chlorine Dioxide Droplets leave less taste than most alternative products but it’s still an acquired taste. Finally, the process is a bit slow if treating a few litres at a time, taking around half an hour for two litres.
Positives: Cheap, small, lightweight
Negatives: Requires clear water, leaves behind ‘chemical’ taste, can be slow
Bacteria: Yes
Viruses: Yes
Gravity Filters
Gravity filters provide a hands-free way to filter water, making them an excellent choice for group camping or base camps. The system typically consists of two reservoirs: an “unfiltered” bag that you fill with untreated water, which hangs above a “clean” container. Gravity naturally pulls the water through a filter element—usually a hollow fibre or ceramic cartridge—removing contaminants like bacteria, protozoa, and particulates as the water flows down. This method requires little effort and allows everyone at camp to access filtered water without manual pumping or squeezing.
The simplicity of gravity filters makes them convenient for those who may be tired after a long day of hiking or want to set up a base camp water source. Many gravity filters can process a large volume of water, some purifying up to several litres at a time, making them ideal for families or larger groups needing more water for cooking, drinking, and cleaning.
One potential drawback of gravity filters is their slower processing time compared to pump or squeeze filters. However, this is often balanced by the fact that they require no physical exertion; you can simply set up the system, go about other tasks, and come back to clean water. It’s also worth noting that while gravity filters are effective at removing bacteria and protozoa, they typically don’t eliminate viruses, so additional treatment may be needed if viral contamination is a concern.
Positives: Hands-free, ideal for groups, processes large volumes
Negatives: Slower than pump filters, doesn’t remove viruses
Bacteria: Yes
Protozoa: Yes
Viruses: No
UV Purifiers
UV purifiers are a high-tech water treatment solution that uses ultraviolet light to neutralise harmful pathogens such as bacteria, viruses, and protozoa. The UV light disrupts the DNA of these organisms, rendering them unable to reproduce and effectively neutralising any potential health risks. To use a UV purifier, simply immerse the device in a clear water container and stir for around 60 to 90 seconds, depending on the device’s specifications and the volume of water. This process is quick and highly effective, killing up to 99.9% of common pathogens without altering the water’s taste or adding chemicals.
UV purifiers are an excellent choice for travellers and outdoor enthusiasts who need a lightweight and efficient way to purify water, especially in areas where clear, pathogen-laden water is more accessible than turbid sources. One consideration is that UV purifiers run on batteries, which may require extras on longer trips, but their compact size and speed make them a top pick for those on the go. Additionally, they work best in clear water, as particles can obstruct the light and reduce effectiveness, so a pre-filter may be needed if the water source is cloudy.
Positives: Quick, lightweight, chemical-free, effective against bacteria, viruses, and protozoa
Negatives: Requires batteries, less effective in cloudy water without a pre-filter
Bacteria: Yes
Protozoa: Yes
Viruses: Yes
Squeeze Filters
Squeeze filters are popular among hikers and ultralight backpackers due to their compact size, ease of use, and efficiency in filtering water on the go. Typically, squeeze filters come as a small, lightweight cartridge that attaches to a soft-sided water pouch or a compatible bottle. To filter water, you simply fill the pouch with untreated water, screw on the filter, and squeeze the pouch to push water through the filter. The filtered water can be consumed directly or transferred to a clean container.
Squeeze filters use materials like hollow fibre membranes, which are highly effective at trapping bacteria and protozoa, ensuring safe drinking water. This method makes them ideal for backcountry areas where viruses are less of a concern, though they may not fully protect against viral contamination. These filters are versatile, allowing users to drink directly from the pouch, fill up a separate water bottle, or even attach the filter to a hydration bladder, adding to their convenience.
One of the few drawbacks of squeeze filters is that they require regular maintenance to perform optimally. Over time, these filters can clog, mainly if they’re used with turbid or silty water. Many models include a backflush syringe to clean the filter by flushing it with clean water, helping extend its lifespan. For best results, try to source clear water using a squeeze filter or pre-filter with a cloth if the water is especially dirty.
Positives: Lightweight, easy to use, great for single travellers.
Negatives: It can be slow, needs regular cleaning to avoid clogs, and is not virus-proof.
Bacteria: Yes
Protozoa: Yes
Viruses: No
Bottle Filters
Bottle filters are an excellent solution for anyone seeking a straightforward, no-fuss water filtration method. These filters are integrated directly into the bottle, allowing you to filter water simply by filling it up and drinking it through the spout. This all-in-one design makes them user-friendly and removes the need for separate filters, hoses, or pumps. Just scoop up water from a stream, lake, or even a questionable tap source and drink directly from the bottle—the built-in filter will remove contaminants as you sip.
Bottle filters appeal to urban travellers, international tourists, and hikers who want quick access to safe drinking water without the hassle of setting up a larger filtration system. The filter elements are typically made from hollow fibre membranes or activated carbon, effectively removing bacteria, protozoa, and sediment, ensuring the water is safe to drink. Some models even include carbon components to improve taste and reduce odours, a bonus when drinking from natural sources.
However, it’s important to note that most bottle filters are not designed to handle viruses, as they often lack the pore size necessary to trap them. An additional purification method may be needed for travellers heading to areas with potential viral contamination in the water. Additionally, bottle filters are usually limited by the bottle’s volume, which may be restrictive for longer outings where more water is required.
Positives: User-friendly, portable, improves taste, all-in-one design
Negatives: Limited capacity, ineffective against viruses
Bacteria: Yes
Protozoa: Yes
Viruses: No
How to Filter Water Outdoors – Comparison Table
|
Method |
Description |
Pros |
Cons |
Best For |
|
Boiling |
Heat water to a rolling boil for 1-3 minutes. |
Effective against bacteria, viruses, and parasites |
Requires fuel and time, does not remove particles |
Emergencies, base camps |
|
Pump Filters |
Manually pump water through a filter cartridge. |
Removes bacteria and protozoa, portable |
Bulky, can be labour-intensive, may not remove viruses |
Regular use, camping, small groups |
|
Gravity Filters |
Uses gravity to pass water through a filter bag, ideal for group use without effort. |
Convenient for groups, no pumping needed |
Slower process, may not remove viruses |
Base camps, large groups |
|
Chemical Tablets |
Dissolve tablets (chlorine or iodine) in water to kill pathogens. |
Lightweight, effective against most pathogens |
Chemical taste, not effective against all parasites |
Ultralight backpacking, emergencies |
|
UV Purifiers |
Use UV light to neutralise pathogens by damaging their DNA, making water safe to drink. |
Fast, effective against viruses |
Requires batteries, doesn’t remove particles |
Solo hiking, short trips |
|
Squeeze Filters |
Attach to a soft bottle or pouch and squeeze water through a filter; portable and effective for bacteria. |
Lightweight, easy to use |
Slow, can clog over time, may not remove viruses |
Day hikes, ultralight backpacking |
|
Bottle Filters |
Built into water bottles, allowing you to drink directly from natural sources with minimal setup. |
Super convenient, compact |
Limited water volume, may not filter all pathogens |
Solo travellers, urban and outdoor use |
All of these methods have their uses and none is necessarily better than the other, but hopefully this gives you a good idea of which is right for you. If you’d rather just shop our entire range of water filters, you can here.
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