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Hands-on Gear Review
Cons: No separate storage for clean and dirty hoses, expensive, hard to collect water from small or non-flowing sources
After some surprising results in our tests, the GravityWorks took the lead in our comparison, winning the Editors' Choice award. We initially thought this system would be bulky and time-consuming, but the opposite was true. In fact, this is the fastest system for filtering water, it is the best option for filtering large quantities, is one of our lightest filter systems, and requires little to no maintenance. The filter lasts a long time before replacement (1,500 liters), being beaten only by the MSR MiniWorks EX (2,000 liters), Sawyer Mini (100,00 gallons) and Sawyer Squeeze (claimed 1 million gallons). Since it easily treats small or large amounts of water, it is the most versatile system, working well for a camp of multiple people or for a solitary hiker on the move in the mountains. The primary drawback to this system is that is more expensive than the average pump filter such as the Katadyn Hiker Pro or the MSR Sweetwater Microfilter. Also, it does not treat viruses like the SteriPEN Adventurer Opti or the First Need XL, so if you plan to travel around some very sketchy water, this may not be the filter system of choice.
This filter just barely beat out its closest competitor, the MSR AutoFlow Gravity Filter. This very similar system may work best for you, especially if you already have an MSR hydration bladder or Dromendary bag to use with it.
RELATED: Our complete review of backpacking water treatment
OutdoorGearLab Editors' Hands-on Review
The GravityWorks is a unique water purification solution in that it combines filtering with storage. It comes in either a 2L size or a 4L size, and the 4L system provides a total of an 8-liter capacity (4L in the dirty bag and 4L in the clean bag). This makes for a convenient and ample water supply for your campsite or for backpackers hiking through a zone with scarce water sources. This means you can eliminate the need to carry a separate water container for campsite water, saving weight and space. In practice, it is fast, easy to use, and makes treated water easy to access whether you are solo backpacking or in a group campsite.
The hollow fiber filter is effective against protozoa and bacteria, but not viruses. For what it does sterilize, this is a very reliable system. It is ideal for backpacking in North America where Giardia is the biggest concern, but would not be the best option for international travel.
The absence of moving or electronic parts means that it is less likely to break or malfunction. Be cautious of letting the filter itself freeze. This could potentially ruin the filter without the user realizing it. We protected against this by tucking the filter element in our sleeping bag on nights we were worried the temps would get below freezing.
Ease of Use
This system is ridiculously easy to use, even more so than a lot of pump systems. You fill the dirty bag, zip the top, attach the hoses with the arrow on the filter pointing towards the clean bag, and set the dirty bag somewhere above the clean bag (it doesn't even have to be very high). This system worked fine with the dirty bag sitting on a rock and the clean bag on the ground, it does not need to be hanging from a tree to operate. However, the 2L system includes a buckle strap (the 4L system has a solid strap) and the buckle makes hanging the dirty bag from a tree especially easy.
After you fill it and set it up, you can let it work its magic while you set up camp or eat a snack. We like that the dirty bag and clean bag are clearly labeled, and the dirty bag has an open zippered top, while the clean bag does not, so you will not accidentally mix them up and cross contaminate. The only downside is that the hoses are not as easy to keep separate. Since the dirty hose has the filter attached to it, they are easy to tell apart, but there is no convenient way to pack them to keep the hoses separated from each other.
Our main complaint is that the top can be incredibly difficult to zip shut, especially if your hands are cold from dipping the bag into a snowmelt stream. In our experience, this zipper gets harder to close the longer you own the filter. It closes like a ziplock bag but with a much larger and harder plastic seal. It can require some serious hand strength to zip shut so that it won't leak.
This filter excels at treating large quantities of water for groups or cooking. The 4L system can store and carry up to eight liters of water at a time, and the whole system can treat an entire gallon in under five minutes. It works very well to set up this system at camp and take water from it as you need it.
Time Before Drinking
At first, we were skeptical of this system. We thought it would be slow and cumbersome to use, but instead we were quite impressed. This gravity system works surprisingly fast. We timed the filtration process in both the 4L and 2L systems. We tried to make it as even as possible by raising the dirty bag so that the hose fell straight to the clean bag with no coil of hose on the ground, making the fall line the same for the tests. It took 1:50 for the entire 2L system to work and 3:05 for the 4L system. We also timed just a single liter moving through the filter, and that took exactly one minute.
This is less time than waiting for tablets to work their magic, and involves less work for the user than any of the pump systems. None of the pumps will provide four liters of treated water in under five minutes. Even the SteriPEN, which is one of the fastest systems, takes 90 seconds per liter. If you do the math, takes six minutes to purify four liters of water, not counting fill times in between sterilizations. Waiting almost five minutes to drink can seem like a pain, but in actuality this GravityWorks system treats the most water the quickest and with the least amount of work.
Including the storage bag, the 4L system weighs 11.99 ounces, which is one of the lightest filters we tested, being beaten only by the MSR Hyperflow Microfilter, the Sawyer Squeeze, and compact straw systems like the LifeStraw and the Sawyer Mini. This makes the GravityWorks a great choice for hiking and backpacking since it does not weigh you down.
Durability/Uses Before Maintenance
The maintenance on this system is very low. The filter is good for 1,500 liters, which is second only to the MSR Miniworks ceramic filter and the Sawyer Squeeze, which are good for 2,000 liters and 1 million gallons respectively. So the Platypus filter does not need to be replaced all that often. In the meantime, the only other maintenance required is a quick and painless back-flush when you set up the gravity system. All this requires is elevating the clean bag above the dirty bag for a couple seconds to let air bubbles escape, which is nothing compared to scraping a ceramic filter or reversing all the valves to set up the complicated back-flush on the MSR Hyperflow.
There are two things to watch out for: do not puncture a hole in one of the bags, which would ruin the system, and don't let the filter unit freeze, which can damage the hollow fiber membrane. However, the bags seem very durable and in our long-term tests where we have used this filter extensively, we have not had an issue with this. It is possible that the MSR AutoFlow Gravity Filter would be more durable, since the bag in that system is made from the tried and true drom bag material found on the MSR Dromlite, but we have found the Platypus bags to hold up to a lot of hard use.
The water flavor remains unchanged and particulate is strained out of the clean water. We find the water through this system to be fresh and delicious.
Differences in the 4L and 2L Systems
Both the 4L and 2L systems use the same filter and draw from the same general principle for using gravity to push the water through the filter. They both feature bags made of durable Platypus plastic and come with a shut-off clamp for the hose. So is the only thing different the size? No. Actually there are a couple of notable differences, mainly in the configuration of the system. Here we list them out for you so you can better decide which one will work best for you.
Credit: Luke Lydiard
Since this system excels at treating larger quantities of water, it is well-suited to car camping or backcountry trips that will involve a base camp. Our initial impression was that it would not be as conducive to fast in-a-day backcountry missions where you want smaller quantities of water quicker, and do not want to sit around for five minutes waiting for it to filter. Then we tried it on our own hiking mission and felt that it took only as much, if not less, time to filter water through this system as with a pump. Even though the bags hold a gallon of water, you can fill the system just part way if you are in a hurry and do not want to carry extra water. Our final verdict: it works well in just about any backcountry situation where you would like to filter water, with perhaps the exception of really nasty shallow pools where scooping up goopy water would be difficult.
At $120, the 4L filter system is on the expensive side, which seems strange for such a simple system. It costs more than even the SteriPEN with its high-tech UV light. It does, however, include storage bags, which could cut your costs on another item. This system is excellent to use and works very fast, so in our opinion it is worth the investment, but expect to shell out a few more dollars for the luxury that the gravity system provides.
Credit: Luke Lydiard
In the end, we felt that the GravityWorks was the best water treatment system available, and the one we'd recommend to friends and family for general use. If you are looking for one water filter that can serve your needs, whether car camping or backpacking, this is the one we'd pick. And, that's why it earned our Editors' Choice Award for best water filter.
You can purchase this versatile filter in either 4L or 2L sizes. For lighter weight get the small version, for more versatility and group camping get the larger version. Below is a comparison of the two different sizes, 2L on the left and 4L on the right.
GravityWorks 2.0L Bottle Kit
GravityWorks 4.0L Reservoir Kit
GravityWorks 2.0L Replacement Hose Kit
GravityWorks Carbon Element
GravityWorks Universal Bottle Adapter
— McKenzie Long
OutdoorGearLab Member Reviews
Most recent review: July 18, 2015
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