Perhaps nothing is more important to a good time outdoors than having a handy supply of fresh, clean water. In fact, MSR’s very first stove—the Model 9—was built explicitly to improve the hydration, and thus the performance, of high-altitude mountaineers. No matter what your goals are, we know that hydration is a key element in reaching them.

Over the years, MSR has built one of the most comprehensive and reliable assortments of water treatment and storage products available. From ultralight and portable solutions for trail ultras to basecamp and emergency purifiers for demanding, high-capacity needs, we’ve got you covered.

Of course, with many options come many choices, and that’s why you’re here. So, let’s dive into a comprehensive overview of what each water filter and water purifier is built for, so you can choose the best solution for your adventures. Armed with a solid understanding of the latest technology and product options, you can easily use the chart below to zero in on the filter, purifier, or combination that best fits your needs.

Model	Weight	Filter Media	Flow Rate	Best Use	Group Size
Guardian Purifier	1 lb 1 oz	Advanced Hollow Fiber	2.5 liters per min	International Travel, Crowded Back and Frontcountry Areas	1-3 people
Guardian Gravity Purifier	1 lb 3 oz	Advanced Hollow Fiber	0.5 liters per min	International Travel, Crowded Back and Frontcountry Areas	3+ people
AutoFlow Gravity Filter	12 oz	Hollow Fiber	1.75 liters per min	Backpacking, Hiking, Vehicle-Based Adventures	3+ people
Thru-Link Inline Water Filter	2.5 oz	Hollow Fiber	1.5 liters per min	Long-Distance Backpacks, Mountain Bike and Gravel Rides, with a Reservoir-Based Hydration System	1 person
TrailShot Water Filter	5 oz	Hollow Fiber	1 liter per min	Ultralight, Long-Distance or High-Speed Missions where Minimalism is Key	1 person
MiniWorks EX Microfilter	1 lb	Ceramic Plus Carbon	1 liter per min	Backcountry Backpacking and Hiking	1-4 people
Hyperflow Microfilter	7.8 oz	Hollow Fiber	3 liters per min	Backcountry Backpacking and Hiking	1-2 people

 

Water Purifiers

The ultimate water treatment devices, purifiers come in two forms: mechanical and chemical. Mechanical purifiers physically remove tiny viruses (and anything larger) via a membrane with pores that are smaller than a virus (0.02 microns). Chemical purifiers simply kill anything living in the water. Mechanical water purifiers are the most convenient to use, with no foul taste, no waiting time (called ‘dwell’ time) for chemicals to take effect, and no need to worry about the right concentration of those disinfectants. However, for very large volumes of water, such as municipal systems and lasting emergency situations, chemical treatment remains the preferred alternative for its ease and cost-effectiveness. (Aquatabs® are also part of an extremely lightweight and essential backup to any mechanical purifier should it become lost or compromised in the field.)

Read more about whether you need a Purifier or a Microfilter.

Guardian™ Purifier

The Guardian Purifier is designed to purify water from the most demanding backcountry sources imaginable, and it does so very efficiently. Originally designed in conjunction with the US military, this highly advanced mechanical water purifier is ideal for global travel, crowded backcountry areas, and for anyone building a home emergency kit. It delivers an impressive 2.5 liters per minute using a traditional pump design, pushing dirty water through hollow-fiber filter media. Unlike traditional pump filters, though, it was engineered with a revolutionary, self-cleaning design, meaning no backflushing or disassembly is required to keep it running optimally. If you’re a visual person, check out this video to see it in action and hear what makes it the purifier you can lean on for the most challenging situations on earth.

Guardian™ Gravity Purifier

Based on the same technology as the original Guardian, the Guardian Gravity Purifier is for anyone seeking similar protection with less work and larger volumes of water. It’s not as fast as the pump version of the Guardian Purifier, but what it lacks in speed, it makes up for in capacity and ease of use. The Gravity version replaces the pump action with a single, 10-liter reservoir that you fill with dirty water. Simply hang the dirty reservoir high enough to get a straight hose between it and the clean outlet and let gravity pull the water through the hollow-fiber filter media for you. A universal adapter on the clean side fits most bottles for your filling convenience. It’s also self-cleaning, requiring just the opening of a valve. As an added bonus, the Guardian Gravity Purifier adds a carbon stage of filtration to help neutralize taste, odors, and organic chemicals.

Traveling internationally? Learn more about treating water overseas.

Water Filters & Microfilters

Water filters and microfilters are the best choices for most trips in the U.S. and Canada where bacteria and protozoa are the primary concerns. These waterborne bugs are roughly ten times larger than viruses, so a microfilter’s pores are sized to match at 0.2 microns. This takes care of all the things you’ve likely heard of, including Giardia, Cryptosporidium, E.coli, Salmonella, and the like, in addition to larger particulates and dissolved solids. Some microfilters are also paired with activated charcoal for two-stage protection, helping to remove chemicals, tastes, and odors from water.

AutoFlow™ XL Gravity Filter

The AutoFlow XL Gravity Filter is essentially the microfilter version of the Guardian Gravity Purifier with some key differences. First and foremost, it’s a microfilter, not a purifier, making it ideal for backcountry use throughout the U.S. and Canada. Like all microfilters that meet the EPA standard, it removes bacteria (99.9999%), protozoa (99.9%), and particulates—the most common contaminants in water. The AutoFlow’s single-stage hollow fiber filter relies on gravity to pull water through the filter media, freeing up your time and talents for other things, and the 10L capacity is perfect for group demands.

ThruLink™ Inline Water Filter

Are you often on BIG days in the backcountry? Does the idea of just stopping to scoop water for a quick refill sound good to you? If so, the ThruLink Inline Water Filter is worth a look. Harnessing the speed and ease of hollow fiber filtration, the ThruLink has been optimized for high flow rates and can be spliced directly into your hydration system. This allows you to drink as you go, with on-demand water filtration. It also has a carbon element that helps eliminate chemicals, taste, and odors and comes complete with all the attachments you need to turn it into a gravity system when you finally do get to camp.

TrailShot™ Pocket-Sized Water Filter

The pocket-sized TrailShot Water Filter takes the idea of minimalism to the next level, delivering clean water with minimal weight, size, and surprising ease. Just drop the intake hose into the water source and squeeze your way to hydration. Even better, it cleans with just a few shakes to keep it running optimally. At one liter per minute and weighing just five ounces, it’s perfect for long XC mountain bike rides, trail runs, and big traverses where speed, weight, and bulk are key considerations for anything that makes it inside your pack.

Hyperflow™ Microfilter

The Hyperflow Microfilter is our original hollow fiber water filter and introduced the world to what this advanced filter media can do. Even with its diminutive size, it gushes an impressive three liters per minute—roughly a liter every 20 strokes—weighs just 7.8 ounces and can fit easily in the lid of a small daypack. It remains one of the fastest ways to get clean water in the backcountry.

MiniWorks® EX Microfilter

The trusted standard in backcountry water filtration, the MiniWorks EX is the best-selling backcountry microfilter on the market for good reason. Its solid, hybrid ceramic and carbon filter element is virtually clog-proof throughout its usable life because you simply scrape away the clogged exterior to reveal a fresh layer of filter media beneath. Mechanically, the pump itself can also be maintained and refurbished in the field, making it the go-to choice for absolute reliability on longer backcountry trips far from home.

Care, Maintenance & Other Pieces to the Puzzle

Optimizing Flow Rates

There’s no consideration of a filter’s worth without talking about flow rate. A filter could make pristine water from mud on Mars, but if it’s not fast enough, it’s useless. Measured in liters per minute, the rates given are always with a new filter under optimal conditions. It goes without saying that results will vary based on the quality of water you’re filtering, how many liters of water you’ve already passed through your filter media, and how good you've been with periodic backflushing and maintenance.  There are two ways to optimize flow rate, depending on the style of water treatment:

1. Backflushing/Cleaning

The method for backflushing and cleaning your filter varies with the type of filter media, but the process is pretty easy once you’ve done it a few times. You can never backflush too much, and it’s especially important with hollow fiber membranes. The more packed the membrane becomes with debris, the harder it will be to flush back out, so do it often, before it gets deeply embedded.

2. Full Extension (Gravity systems)

You’ll get the best performance out of your gravity system by lifting the system high enough to get straight tubes between the dirty reservoir and the clean reservoir/outflow point. The difference between a fully extended system and one even partially straight is significant, so if you want better speed, hang ‘em high and straight.

4. A Note on Hollow Fiber and Air

We often hear people say that their brand new hollow fiber filter is really slow. This can be frustrating given that it's new and you had hopes of realizing the speed they offer. However, 99.9% of the time, this is the result of starting with a dry filter and/or air being trapped in the filter.

New filters, or ones that have sat for a long time and dried out, are full of air. The membrane will not pass air, so the fibers appear to be going slowly. Two things will help:

First, you should always test your gear at home before you head out into the backcountry, right? RIGHT?? Doing this will pre-wet your fibers, and you can get the "slow" part over with at home. It can take a few liters of slow filtering before your filter is fully wet, so be patient, and do it before you leave home!

Second, be sure to "burp" your gravity system each time you use it. Even when wet, the empty hose on the dirty side of your system will force air into the filter, slowing the process. Be patient while a small amount of water accumulates on the Clean side of your system; you just need a few hundred milliliters. Then lift the Clean side of the system above the dirty side to reverse the flow, just as you would when backflushing. You can even gently roll the Clean side reservoir to help push the water back through the system. You'll see a stream of bubbles come out of the filter and back into the Dirty reservoir. Tap the filter housing to be sure all the air bubbles release = from the fibers, and when they stop, lower the Clean side again; you will see a dramatic improvement in speed. 

Integrity Checks

Because it’s impossible to visually tell the difference between water with and without microbes present, each MSR filter and purifier comes with instructions for an integrity test to ensure that your system is doing its job. Ideally, you’ll run one of these simple tests before each trip or after an incident that could potentially affect your filter media. Depending on your filter, such things as a hard drop, being frozen overnight, or a mechanical issue could affect its efficacy. Do the test and take the guesswork out.

Long-Term Storage

It's worth remembering that you are using your filter to remove all sorts of things you don't want in your water. It makes sense then, that prior to storing your filter for extended periods (more than a week or two), you should sanitize it. This is good practice for all filters, but especially true for Hollow Fiber filters that can't be dried effectively.

Aside from neutralizing anything nasty inside, the most common issue is a slime mold that can grow in a wet filter, clogging the filter media. To prevent this, it’s a good idea to run a weak bleach solution (1-2 drops per liter) through them before putting them on a shelf to ensure nothing grows inside. Again, follow the instructions provided with each filter, and you’ll be all set for your next trip.

Backup Water Storage

Having backup storage can make camp life easier and your filtering chores far more efficient, especially in basecamp and group situations or when your water source is far away. Check out our extra burly Dromedary® Bags for expeditions and road trips, or our lightweight DromLite™ Bags for backpacking and other times when space and weight are priorities. Gravity systems also allow you filter on-site, and then bring back a full reservoir of dirty water that you can filter on-demand back at camp.

Plan B for Water Treatment

Just as you bring a pole splint for a broken tent pole or spare batteries for your headlamp, having a backup plan for a compromised or exhausted water treatment system is an essential part of any trip. It could be as simple as an extra filter cartridge, spare parts for pumps, or the lightest and most compact backup: a handful of Aquatabs® to chemically treat your water in an emergency. However you filter, be sure to have a backup or a way to fix what’s wrong; no one wants a trip to end dehydrated or with waterborne illness.

Related Posts:

• MSR’s Complete Guide to the Basics of Water Treatment
• Backpacking Water Filter vs. Water Purifier: What’s the Difference?
• Clean Water Solutions to Prepare for Emergencies

Updated. Originally Published May 6, 2021.