A Water Filter Built for Those Who Move: HydraPak PackFlask Review

I heard a backpacker say recently that the best backpack is the one you never have to take off, and the same idea applies to water filters. The best water filter is one you can use without breaking your stride and without thinking. The easier it is to drink water, the more likely you’ll be to actually stay hydrated. After using the HydraPak PackFlask ($72) for the last 4 months, it’s become the water filter that I reach for over and over again.

The PackFlask combines a lightweight 750mL soft flask with a water filter integrated with a high-flow, self-sealing nozzle. You fill the flask, screw on the water filter/nozzle, and you’re good to go.

In short: For trail runners, speedy backpackers, and day hikers who roll solo and want a no-fuss filtering option, the PackFlask is an excellent choice. It’s possible to keep moving and drink water one-handed, giving you no excuse not to stay hydrated.

Looking for a new water filter? Check out how the PackFlask compares to the rest of the market in GearJunkie’s Best Backpacking Water Filters Buyer’s Guide.

HydraPak PackFlask: Review

Testing

I used the PackFlask as my primary water filter for three backpacking trips this summer. I covered 96 miles on the Oregon Coast Trail, 95 miles in Yosemite, and 60 miles in the Black Forest in Germany.

On the Oregon Coast Trail, I had regular access to clean drinking water from public fountains, so I didn’t always need the filter. Other times, like in Yosemite and Germany, I regularly filled up the flask from lakes and streams.

Soft flasks typically make me a bit nervous when it comes to durability, but the HydraPak one held up well. After all my trips, I saw no noticeable damage. The slightly wider mouth also made it easier to clean. When I got home, I would swish some clean water around the flask, and then prop it up on a spoon or knife handle to air it out, and it never got that distinct “funk” or smell that some bottles get.

Ease of Use

I loved just how easy this filter is to use. I would dunk the flask in a stream, fill it up, screw on the filter/cap, and be good to go. The nozzle is the same kind that you find on sports water bottles; You simply suck a little and get water. The nozzle is self-sealing, so you don’t have to worry about leaking. I tossed the sealed flask around, turned it upside down, and no water came out.

More and more packs these days have shoulder pockets, and the 750mL flask was the perfect size to fit in these pockets. The filled flask fit in the shoulder pockets on my packs from Six Moon Designs and Redpaw Packs. If you don’t have a pack that has shoulder pockets, the product also includes a mesh pocket that you can Velcro onto the shoulder strap of any daypack.

This setup meant I could drink water with one hand. I’d flip open the cap, suck some water, put the cap back on, and continue hiking along. Many packs have large water bottle pockets on the side, but if you’re someone like me who hikes alone frequently, it can be difficult to access these. Sometimes it feels like I’m about to dislocate my shoulder trying to put my bottle back in one of these pockets.

This ease was clutch on really big uphills. In Yosemite, I would be gasping as I climbed 1,000 feet at a time up rocky terrain, and I could bend my head down, gulp down some water, and then keep moving. I hate stopping on big climbs to take off my pack, but I also can’t survive a long ascent without needing some H20. The HydraPak filter was the perfect solution.

The nozzle also made it easier to drink and keep hiking. If you’ve tried to walk and drink out of a wide-mouth Nalgene at the same time, you’ve undoubtedly spilled water all over yourself.

As the flask gets to about half-full, sucking up water becomes a bit harder. When this happened, I would (still one-handed) use the crook of my elbow to squeeze the flask and push up water, which worked well.

When the flask would empty, I would stop and refill it with water from the two large water bottles I was also carrying. I repeated this small task every 2 hours or so on trail, which was fine, since I stop that often anyway to go to the bathroom or have a snack.

The 750mL capacity means it’s also quite easy to add another water bottle to your lineup without taking up space or adding weight. With two 1L bottles from Mazama and CNOC, plus the HydraPak flask, I was carrying 2.75 L at a time, so I didn’t have to worry about running out of water.

Drawbacks

Best for Solo Use

When it came time to cook my dinner, I would use the PackFlask as a typical squeeze water filter, squeezing clean water into my pot. Since I was alone, I typically didn’t need more than 750 mL of clean water at once. However, if I were in a big group, prepping dinner would’ve meant a lot of squeezing, refilling, and squeezing again. If it’s more than just you, a squeeze or gravity filter with a 2L or 3L capacity is obviously much more efficient.

As someone who does almost all of their backpacking alone, this isn’t a big con for me. But if you’re someone who backpacks solo, in pairs, and with groups, I’d look for a more versatile filter.

Doesn’t Play Nicely with Others

I’ve used the Sawyer Squeeze filter for years, and one of its assets is the fact that you can screw it onto SmartWater or other similar bottles, basically making any water bottle a filter. The HydraPak filter, however, doesn’t screw onto any bottle except the provided soft flask. I tried to attach it to my narrow-mouth Nalgene, Mazama, and CNOC bottles, and none of them worked. By buying this filter, you’re committing to using HydraPak’s flasks and bottles.

Not Suited for Winter

HydraPak warns that freezing temperatures may compromise the hollow fiber of the membrane. It advises customers to keep the filter in their pocket or near their body if they are in cold temperatures. If you do a lot of winter backpacking or other cold-season recreation (or go into alpine environments), this is something to be aware of.

How Does the PackFlask Stack Up?

At 2.7 ounces (without the Velcro mesh pouch), the HydraPak is one of the lightest filters on the market. It weighs less than the Platypus 1L Quickdraw (3.3 ounces) and the Sawyer Squeeze with 750mL soft flask (3.4 ounces).

Its filter life (1,500 L) falls squarely in the middle of the pack. It lasts longer than the Platypus Quickdraw (1,000 L), but not as long as the LifeStraw Solo (2,000 L).

When it comes to price, the HydraPak is at the top of the list. The $72 price tag is more expensive than larger-sized filters from leading brands like Sawyer ($64 for the 2L size) and Kataydn ($53 for the 1L Be Free). It’s only an extra $10-20, but there’s nothing that exceptional about this filter that justifies that higher price.

Conclusions: Who Is the HydraPak PackFlask For?

Folks going out on long day hikes or short backpacking trips should bring a water filter, but carrying along a 3L gravity setup can feel like overkill. The HydraPak PackFlask is a great pick for this scenario. If I were about to go on a 10-mile hike, I’d bring along this filter (along with a few other filled bottles) as a just-in-case option.

I never thought I would become a soft flask fan, but the HydraPak system won me over. Being able to stick it in the shoulder pocket of my pack truly made me more likely to drink water than ever before. For solo backpackers like me who never need that much water at one time, it’s hard to beat the convenience, ease of use, and speed of the PackFlask.