A fundamental necessity of any backpacker’s gear cache is a water filter. Anyone spending more than a day or so in the field runs into the problem of procuring, treating, storing, and transporting water.
Outdoor gear brands have responded to this challenge with countless products, but few match the simplicity, durability, and value of the Platypus GravityWorks water filter system. While this filter system is not without its shortcomings, I have used it extensively in backcountry settings and found it to be among the most useful items in my kit.
The Platypus GravityWorks water filtration system is lightweight, easy to use, and equally useful in the backcountry as it is at basecamp. It filters water fast and allows you to transport a lot of it. While not as durable as some alternatives, it’s a safe choice for reliable water filtration.
My experience with the Platypus GravityWorks filtration system extends back a decade, during which I worked on trail crews throughout the Northwest. It was our crews’ method of choice to treat and store water throughout several work seasons, so it’s not an exaggeration to say I have stuffed and unstuffed this thing from a pack well over a hundred times.
Although I’m no longer in trail work, I recently tested the newest available version during an overnighter in Boise National Forest in preparation for this review.
The Platypus GravityWorks water filtration system comes in several sizes, including 2-, 4-, and 6-liters. The product described in this review is the 4-liter version.
Regardless of its particular size, the system consists of three basic components: a dirty reservoir for the collection of untreated water, a microfilter, and a clean reservoir for treated water. Also included are hoses to connect these components and a mesh carrying bag to keep them together. The carrying bag has two separate pouches to segregate the clean and dirty reservoirs during storage.
I appreciated that every element of this system’s design is intended to prevent cross-contamination from the dirty reservoir to the clean.
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Simple Features Make For Easy Setup
Filling the dirty reservoir is a process made easy by a couple of simple features.
- Wide Mouth: The reservoir has a wide mouth to expedite collection. The plastic around the mouth is stiff and thick, so you can shape the mouth to catch even a small trickle of water.
- Sturdy Handles: For use in swift water, you can hang onto the dirty reservoir’s sturdy handle to prevent it from slipping away in the current. Both reservoir bags are equipped with carrying handles to aid in transport.
- Narrow Shape: The long, narrow shape of the dirty reservoir allows you to immerse it in shallow water if this is your only available option. I had the advantage of collecting relatively clear water from the Middle Fork of the Payette River on this occasion.
Once you have collected the untreated water in the dirty reservoir, you can assemble the rest of the system.
The assembly is straightforward and intuitive. The hose attaches to the dirty reservoir with a sealed, click-in mechanism. Arrows and signage on the filter itself indicate the proper direction of flow.
Among others, these features characterize my favorite thing about this product: its simplicity and ease of use. There is exactly one way all of this stuff fits together, and it would be impossible to make it any clearer.
How the Platypus GravityWorks Filter Works
Below the filter, a long rubber tube connects via screw-cap to the clean reservoir. Once all these parts are securely attached, the filtration process is as simple as elevating the dirty reservoir above the clean reservoir. Gravity does the rest, pulling the dirty water through the filter.
I find it best to hang the dirty reservoir by its handle from a limb or a Staub, but options abound.
A personal observation (and frequent complaint in reviews of this product) is that the filtration process is slow to begin. This is likely due to the presence of either:
- air bubbles in the dirty line, or
- debris and sediment clogging the filter.
You can eliminate or at least reduce this problem by backflushing. To do this, elevate the clean reservoir above the dirty reservoir to reverse the water flow backward through the filter. This flushes the filter and forces air bubbles out of the line. This seems like a facile solution, but it had observable results for me. You should be prepared to do this every single use.
Modularity and Accessories
It’s worth mentioning that the clean reservoir is designed to function similarly to a CamelBak. Its long, narrow shape is ideal for sliding into the hydration pouches built into most modern backcountry packs.
Platypus also sells separately an inexpensive drink tube kit (highly recommended) that connects the clean reservoir directly to your parched mouth. This is only one instance of the system’s extensive modularity, which can be expanded with lots of accessories available for sale from Platypus.
Is the Filtered Water Clean?
As to the filter’s efficacy in treating water, it’s obviously difficult to judge without scientific instruments. What I can say with absolute confidence, however, is that I have personally used this product to filter hundreds of liters of water from various rivers, lakes, and streams and have never experienced a hint of illness.
The manufacturer rates the filter’s lifespan at 1500 liters. During my seasons of heavy use with this system, I replaced the filter once a year as a matter of course.
What I Like About the GravityWorks Filtration System
1. Compact and Lightweight
The Platypus GravityWorks system is small and lightweight. This is an obvious concern to backpackers. Space is limited in your pack, and you want to make every ounce count. All told, the whole system weighs in at 11.5 ounces, and its physical bulk is pretty negligible. The only element with any real bulk is the filter component itself; the reservoir and tubing can be wrapped and stuffed around it.
2. Filtration Speed
The manufacturer’s claimed filter rate of 1.75 liters per minute is close to accurate. At this rate, one would expect 4 liters to filter in about 2 ½ minutes. I timed 4 liters at 2:48. The filtration speed will depend, of course, on the age of the filter, the quality of the water, and the regularity of maintenance or backflushing.
3. High Capacity
The GravityWorks system includes 2 reservoirs, which doubles your water storage capacity. The 2-liter system can store 4 liters, the 4-liter system can hold 8 liters, and so on. This doubled storage capacity which is a simple, but considerable, advantage over Katadyn, one of Platypus’s main competitors.
4. No Moving Parts
No moving parts are the selling point that clenched me. After pulling a crosscut saw all day, my body has tremendous resistance to pumping water through an MSR pump filter. I’d much prefer to sit back, relax, and let gravity do the work while I gnaw on an uncooked Ramen brick.
The reservoirs are marked “CLEAN” and “DIRTY” in giant block letters to avoid confusion for attentionally-challenged persons like myself. In older versions of the product, both the clean and dirty reservoirs had large openings with zip closure. However, in the most recent product iterations, the clean reservoir has only a small opening that connects via a tube to the filter. This feature is designed to reduce further the chances of confusing the dirty and clean reservoirs. The direction of the water flow is also clearly indicated on the filter.
What Could Use Some Improvement
1. Not Super Durable
It could be more durable. As the durability of the plastic reservoirs has never presented a problem for me, I don’t want to cast aspersions unduly. The heavy-duty plastic of the reservoirs is adequate for the task. But the good old Nalgene bottle is still at the top of the heap when it comes to toughness.
2. Requires a Lot of Backflushing
The filter requires a lot of backflushing. Given the significant advantages of the GravityWorks system, I can live with this, but it’s worth mentioning. Due to air bubbles in the line or the accumulation of debris in the filter, the system requires frequent backflushing. By frequent, I mean basically during and after every use.
3. Poor Seal on Dirty Reservoir
You can’t seal the dirty reservoir well on the new versions. This was a huge bummer. The dirty reservoir has a wide mouth, which is incredibly useful for collecting a large amount of water quickly, but…it won’t stay closed.
As mentioned above, Platypus advertises the large storage capacity of this system as a selling point: “Store four clean liters to drink and four dirty liters to filter later.” While this is true, the problem is the difficulty transporting and storing the four dirty liters in a container that doesn’t seal.
My older version of this system had a handy lock that slid on over the mouth of the dirty reservoir and sealed it securely enough to toss into a pack and forget about. The new generation is inexplicably lacking this feature, which is a significant oversight on Platypus.
It should be noted that Platypus continues to make and sell reservoirs with the locking feature (its Big Zip product line), which one could theoretically substitute for the dirty reservoir. But should you really have to?
Comparison to Competitors in its Class
In evaluating the Platypus GravityWorks system, it’s helpful to compare it to competing products. The competition with which I am most familiar is the Katadyn BeFree system (a wedding gift, alas!).
While the Katadyn is a reasonably good system and quite similar to the Platypus GravityWorks, the latter beats the former on a couple of crucial performance points:
- The Platypus system includes a backpack-ready reservoir for clean water, while the Katadyn has no such feature.
- The filter placement on the Katadyn system is poorly designed compared to that of the Platypus.
In the Katadyn system, the water filter, including its outflow port, screws directly into the dirty water collection bag. If you immerse this bag in untreated water, you expose the filter’s outflow port to possible contamination. With the Platypus system, this type of cross-contamination is impossible due to the filter placement farther downstream of the dirty reservoir.
I haven’t observed any significant difference between the flow rates or filter functionality between the two products. However, the issues above are palpable enough to give the Platypus system a pretty firm lead over the Katadyn.
As such an indispensable piece of gear, the Platypus GravityWorks filtration system ticks all the boxes. Its durability, lightweight, and ease of use are, in my view, unmatched among its competition. While the system is not without its flaws, it’s the best I’ve found for treating water quickly and reliably in the backcountry.
With the ability to filter water at reasonably high volumes at a fast speed, the Platypus GravityWorks filter system will also be helpful in an emergency preparedness kit for the car or home. However, this product is best suited to its intended users: backpackers on overnight and multi-day excursions.
I recommend dropping the extra 12.95 on the drink tube kit to make the most of this product. Happy hydrating!