4 Portable Water Filters for Trail Running

Remember the saying from childhood, “Don’t eat yellow snow”?

Well, the saying for trail runners goes like this: “Don’t drink straight from mountain streams.”

Clean and clear as that pristine alpine water may look, ample waterborne bacteria and protozoa lurk in rivers, lakes and trailside puddles everywhere. Cases are rare, but it’s not unheard of for those opting to drink straight from water sources in the outdoors to contract a nasty case of giardia or other waterborne bacterial infection.

Water filters designed for backpackers often weigh around a pound, and are too bulky to fit into a hydration pack. Iodine or water-purification tablets, though undeniably compact and lightweight, can take anywhere from one to four hours before being effective.

What’s a trail runner to do?

With the emergence of several portable, lightweight and fast-acting water filters in recent years, trail runners no longer have any excuse not be “better safe than sorry” on long adventure runs or fastpacking trips in the backcountry.

Here’s the scoop on four trail-runner-friendly water filters.

1. LifeStraw

• Cost: $20
• Weight: 2 ounces
• Filter-Pore Size: 0.2 microns
• Capacity: Up to 264 gallons
• Removes: 99.9999% of bacteria (e.g. salmonella, cholera, E.coli) and 99.9% of protozoa (e.g. giardia, cryptosporidium) (verified)

The premise of the LifeStraw is simple. Put one end directly into a mountain stream or pond and drink from the other.  As one of the lightest-weight filters on the market, you’ll hardly feel it in your pack.

It’s exceptionally easy to use, with handy, attached caps (i.e. you won’t lose them!) on both ends and a detachable lanyard. Not to mention it’s kind of fun to use, too. Kids especially—including the “young at heart”—may get a kick out of the novelty of it; what’s more fun, after all, than pretending that pond is a tasty milkshake worthy of slurping up?

With no batteries to worry about and a virtually endless shelf life until the lifetime capacity is reached (you’ll know when this happens because water simply won’t flow through the filter any longer), it’s a highly reliable product.

The LifeStraw does require somewhat aggressive sucking to get water flowing through—a bit of a downside if you’re either extremely winded or extremely thirsty when you arrive at your water source.

While the LifeStraw is ideal for those running along or near constant water sources, it’s less practical if you’ll only encounter sporadic water sources and want the ability to refill an entire hydration reservoir in one go. LifeStraw has also recently released the LifeStraw Go, a 23-oz refillable bottle with an embedded straw filter—a brilliant innovation we hope they’ll eventually develop into a more runner-friendly handheld bottle or hydration-pack reservoir.

Karma bonus: For each LifeStraw product you buy, LifeStraw provides one school-age child in a developing country safe drinking water for an entire school year.

2. Sawyer MINI Water Filter

• Cost: $25
• Weight: 2 ounces
• Filter Pore Size: 0.1 micron
• Capacity: Up to 100,000 gallons
• Removes: 99.99999% of bacteria, 99.9999% of protozoa and 99.9997% of viruses (e.g. Hepatitis A, SARS) (verified)

We awarded this one Gear of the Year at the end of 2013, and our love affair with it hasn’t diminished in the slightest since. A two-ounce rendition of the original 3.5-ounce Sawyer Squeeze Filter, the MINI is tied in this review for the lightest weight, and is also nearly half the length of all three other filters reviewed here.

It boasts the most versatility of all the filters we tested here, too. It comes with a 16-ounce reservoir that can be filled with water from a stream or lake—screw on the filter, aim it into your mouth, handheld bottle or hydration-pack reservoir and gently squeeze for about one minute.

It also comes with a thin, flexible but durable straw if you prefer to drink directly from water sources. If you have a narrow-mouthed bottle, it can screw directly onto that. Or, perhaps most innovative of all, it can be embedded inline in a hydration-pack drinking tube.

The MINI comes with a syringe that allows you to clean it via backwashing, so there’s no need to purchase replacement cartridges over time as with comparable filters. With no batteries to worry about and 50-380 times as great a capacity (in terms of gallons it can filter in its product lifetime) as any other filter reviewed here, it’s one of the most reliable filters on the market.

Our favorite aspect of the MINI, though, is its extraordinarily compact size.

One caveat: the provided squeeze pouch can pop or tear if too much pressure is applied. Use gently and do not try to wring it out after use.

3. Renovo Trio

• Cost: $44
• Weight: 3.5 ounces
• Filter-Pore Size: 0.05 micron
• Capacity: Up to 264 gallons (or more with $10 replacement cartridges)
• Removes: 99.99% of bacteria and protozoa (verified); Also claims to reduce viruses (unverified) and heavy metals and chemicals (verified)

The Renovo Trio is one of the newest filters on the market—we saw it for the first time at Outdoor Retailer last summer—and it boasts a few features above and beyond the offerings of all other filters reviewed here.

The “trio” in its name comes from its three levels of filtration. First, a small “pre-filter” at the tip with 5-micron fibers that initially remove large particulates (dirt, mud clumps or small rocks) from especially filthy water. It comes with four replacement cartridges for the pre-filter.

Second, the 0.05-micron hollow-fiber membrane (significantly finer than the other reviewed here) filters out bacteria. Third, a carbon-impregnated fiber right at the mouthpiece absorbs final contaminates.

This combination allows the Renovo to remove not only bacteria and protozoa as the other filters in this review, but also heavy metals and chemicals such as arsenic, lead, mercury, pesticides, diesel and chlorine. This is the filter you want when the apocalypse arrives!

It comes with a 750-milliliter (about 25 fluid ounces) reservoir that can be filled with water from an outdoor source. Much like the Sawyer filter, it works by gently squeezing water from the provided reservoir through the filter and into your mouth, handheld bottle or hydration pack.

Renovo claims to have a “large surface area that enables a high flow rate,” though in our testing, we found the flow rate to be a bit slower than comparable filters—nearly three minutes of trickling output to filter approximately 16 ounces of water.

One other small design tweak we’d like to see in future versions of the Renovo Trio: the filter cap is attached—a positive for not losing it—but, frustratingly, it dangles in the way of the filter stream.

4. SteriPEN Classic 3

• Cost: $70 (+ requires 4 AA batteries, not included)
• Weight: 6.3 ounces with batteries
• Filter-Pore Size: Not applicable; works via UV filtration
• Capacity: Up to 13 gallons on alkaline batteries; up to 40 gallons on lithium batteries; lifetime filtration of up to 2,113 gallons
• Removes: 99.9% of bacteria, protozoa and viruses (verified)

The SteriPEN eschews the more common hollow-fiber-filtration approach of the other three products reviewed here for a different approach. SteriPEN uses a battery-powered, miniature UV lamp to filter out waterborne bacteria, protozoa and viruses.

It’s easy to use: insert four AA batteries, remove the cap, dip it into your handheld bottle or hydration-pack reservoir, press the start button and stir it gently for 48 seconds (for a half-liter) or 90 seconds (for a full liter) to purify your water.

You may feel a little like Luke Skywalker wielding your SteriPEN once it lights up with its light-saber-esque beam in your water vessel!

Unlike previous renditions, this third version of the SteriPEN Classic is watertight, so you don’t have to worry about dropping it in your bottle or its batteries being damaged if you get caught in a rainstorm. Though it can work with alkaline, lithium or NiMH batteries, lithium batteries are highly recommended since they’ll last for three times as many filtering sessions.

The Classic 3 also comes with a Pre-Filter, a circular filter that fits on a wide-mouth bottle to remove large particulates (dirt, mud clumps or small rocks) that could interfere with UV filtration.

SteriPEN is a long-beloved favorite for many trail runners—and it’s been around since 1999. However, beware its heavier weight; it boasts a 2.9-ounce product weight, but with the mandatory set of four AA batteries, we weighed it at 6.3 ounces.

For $100, a SteriPEN Ultra is also available—slightly smaller, with an internal battery (rechargeable via computer, outlet or portable solar panel) and weighing in at just under 5 ounces.

From left to right: Sawyer MINI (shown here with optional straw), LifeStraw, SteriPEN Classic 3, Renovo Trio.