Platypus GravityWorks Review

Water Quality

If you're after pure, fresh, and clean drinking water that's free of most water-borne pathogens, the Gravity Works 4L won't let you down. This hollow fiber filter is loaded with an absolute pore size of 0.2 microns, which Platypus claims will filter out all bacteria and protozoan lifeforms, including Giardia and Cryptosporidium. We partnered with independent SGS Labs for third-party testing, which confirmed these claims. The GravityWorks filter removed >99.9% of bacteria and beads that represented Giardia and Cryptosporidium.

To our surprise, the SGS results also revealed that the filter was capable of eliminating >93.6% of the virus contained in the water sample, a claim not listed by the manufacturer, but likely due to the pore size included with the hollow fiber filter. This is a nice bonus, but how you interpret this result is up to your discretion. If you plan on traveling to countries where viruses are more common in water sources, purchasing a filter that's specifically designed to remove viruses is the safest option. It only takes one to make your belly start rumbling.

In addition to the lab results, we loaded this filter up with everything from clear, moving water sources to stinky, murky puddles. Like many gravity filters, it performs best when the water is clear and it does a decent job of eliminating smells. However, when testing it with high sediment it clogs easily after just 2L. You will need to pre-filter to avoid this. See the tip below.

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Ease of Use

We love the user-friendly design of the GravityWorks system. In fact, we had the filter set up and ready to go in less than two minutes. We love the intuitive labeling on the storage bags of “blue” for clean and “black” for dirty. Large openings on the top of the bags make for easy filling, and large plastic buckles make it easy to hang the bags from tree branches or large boulders depending on the setting of your campsite. The valve on the filter is one-way and will not flow until you attach the hose between the two storage bags. The only downsides we can identify with this system are that the “ziplock” type closures can be difficult to fully close over time or during cold weather conditions, as well as the large, flexible opening, which can make it difficult to fill these bags in shallow water sources without scooping up a bunch of sand or dirt.

We love the two-bag system that allows you to “camel up” and store dirty and clean water between water sources, as well as the location of the hose and filter, which allows the system to filter every last drop that you collect. Overall, this filter offers a versatile setup that's intuitive and easy to use whether you're trying to hydrate a small group, want to set up a hand washing station before dinner is served, or even use it as a shower after a long day.

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Durability and Maintenance

The GravityWorks features a high-quality and durable design. The thick plastic bags have beefy closures that resisted punctures despite heavy use during our testing period. We even noticed that the filter itself is covered in rubber on either side, which protects the sensitive hollow fibers if it is (accidentally) dropped on harder surfaces. We also recommend wrapping the filter inside the reservoir bags as another protective measure when packing between campsites or in your suitcase. And if you're planning on camping in colder temperatures, be sure to toss the filter inside your sleeping bag, as it is not freeze-resistant. If it freezes, it could damage the fine interior fibers without showing any signs of damage on the outside.

Platypus recommends backflushing the system after each trip to maintain optimal flow. Luckily, the maintenance procedure is relatively simple. When the flow rate is noticeably slower, simply flip the system and allow the clean bag to flow into the dirty side to flush any clogged sections of the filter. The process is complete when the bag is empty; flip the filter over to see the increased flow rate. If backflushing is no longer successful, this is the filter telling you that it's time for a replacement. If you find yourself adventuring in places like the Colorado River or any glacial-fed streams heavy with minerals, we highly recommend pre-filtering through a t-shirt or a pot to prevent heavy sediment from prematurely clogging the GravityWorks filter. Another small drawback to this system is the difficulty we found in drying out each component once we got home and it was time to clean and store the filter. It often required a few days of thoughtful hanging to remove water from inside the filter, the tubes, and the storage bags. That said, we found all the components durable enough to keep this filter in rotation for many adventures to come.

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Treatment Time

The best part of this filtration system is the hands-free design that allows you to set up the system and walk away while gravity does the work. The GravityWorks's flow rate is among the most consistent that we've tested, easily providing one liter of water in less than a minute, and four liters in less than 5 minutes on average. Although this rate doesn't measure up to the advertised flow rate of 1.75L/min, we can appreciate the consistency, even as the bag reaches low volume toward the bottom of the dirty water bag.

The design maximizes the gravity system by placing an outlet at the bottom of the dirty bag and mounting the filter high, allowing the system to absorb every last drop of collected water for efficiency and faster flow. You can set up and continue with other chores around camp while gravity provides four liters of water in less than 5 minutes. This is great if you're setting up for camp and have time to wait. The drawback is that the flow rate is quite slow if you are trying to refill your bottles and get back on the trail. The flow rate also slows significantly if you don't have a good tree or boulder to hang the bags from; if you aren't able to find the optimal in-line setup, the filter can take over 2 minutes to provide one liter of clean water.

Weight and Packability

The GravityWorks system has a capacity large enough to keep 4-5 people hydrated while remaining packable and relatively lightweight at 11.5 ounces for the entire system. It also packs down easily to 12" x 5 1/2" x 3", or roughly the size of a Nalgene water bottle, which doesn't take up much space inside your backpack.

So long as you're not after the lightest or fastest filter, the GravityWorks takes the cake in backcountry convenience. Although the design has more parts than some others, the provided mesh stuff sack helps you keep track of the components without cutting off airflow. Of all the gravity-fed filters that we've tested, the GravityWorks features a competitive weight and packable size that makes it an easy choice for your next outing.

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Should You Buy the Platypus GravityWorks 4L?

In our experience, the Platypus GravityWorks 4L is the best pick if you want ultimate camp convenience. We love the hands-free convenience and efficient flow rate. The user-friendly design, exceptional quality, and extended filter life make it a worthy investment. While the long-lasting design may require a replacement cartridge now and then, the cost is minimal considering it provides up to 1,500 liters of clean drinking water. If you're looking for a solid return on your investment along with a convenient and reliable gravity-fed system, we highly recommend the GravityWorks for your next adventure.

What Other Backpacking Water Filters Should You Consider?

There are a few other notable systems for you to consider. The LifeStraw Peak Gravity 3L is great option for those after something more affordable, however, it's a bit harder to fill and it doesn't come with a clean water storage vessel. The smaller size is also better for groups of 2-3. The Waterdrop Filter Straw and Gravity Bag is an even more affordable option with an excellent capacity for dirty water; however, some of the components feature limited durability, and the location of the filter makes it difficult to rig the system for optimal flow.