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Platypus GravityWorks Review

Backpacking Water Treatment

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Editors' Choice Award
Price:   Varies from $109 - $120 online  —  Compare at 4 sellers
Pros:  Fastest treatment time, easy to use, lightweight, requires little maintenance, can treat and store up to 8L.
Cons:  No separate storage for clean and dirty hoses, expensive, hard to collect water from small or non-flowing sources.
Editors' Rating:     
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Manufacturer:   Platypus


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). 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 Ultra or the MSR Guardian, 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 Dromedary bag to use with it.

RELATED: Our complete review of backpacking water treatment

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Analysis and Hands-on Test Findings

Review by:
Jessica Haist
Review Editor

Last Updated:
August 10, 2016
The GravityWorks is a unique water purification solution in that it combines filtering with storage. It comes in either a two-liter size or a four-liter size, and the 4L system provides a total of an eight-liter capacity (four liters in the dirty bag and four liters 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.

Performance Comparison

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The Platypus GravityWorks and the MSR AutoFlow are both great options for group camping purposes. Seen here below Mount Whitney.


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.
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The Platypus GravityWorks and the MSR AutoFlow's filters appear to be the exact same product.

The maintenance on this system is very low and the Platypus filter does not need to be replaced all that often. This painless process involves flipping the filter unit so that the direction of flow through it is reversed and letting at least a liter of clean filtered water go through the other way. We discovered that when the filter is having a lot of use in a group setting, it is best to backflush a full four liters through the filter for maximum efficiency. You can just walk away and do something else while it is flushing, but don't forget to flip the filter back around when you're finished back flushing! This is nothing compared to scraping a ceramic filter or the complicated back-flush on the Lifestraw Mission.

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The GravityWorks system is simple and low maintenance. The arrow on the filter shows the direction of flow, and it lasts for 1,500 liters.

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.

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.
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Luke Lydiard using the GravityWorks to rehydrate after coming down from Clyde Minaret in the Ritter Range. The whole system works surprisingly fast, so it is useful even for hikers on the go.

After you fill it and set it up, you can let it work its magic while you set up camp or eat a snack. One of our favorite things about the GravityWorks is that you can have a bag of clean water already filtered on-deck and ready for someone to just pour into their bottle of hydration system; you then have the dirty bag ready to refill right away. This makes getting water filtered for large groups very easy and quick. 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.

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Scooping water into the GravityWorks. Unless the source is a really small puddle, this filter is the easiest to use and the fastest working filter.

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.

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The most difficult part of using this filter is zipping the top shut, which becomes more difficult the longer you own this system and is especially difficult in the cold.

Treatment Capacity

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.
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The three bags for the three gravity filters we tested. (L to R) The 4L MSR AutoFlow, 2L Platypus GravityWorks, 4L GravityWorks. Each one seems durable and fairly easy to use.


This gravity system works surprisingly fast. We timed the filtration process in both the two and four-liter 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.
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We like the clearly marked clean bag that we can use to fill various items around camp, this is the slight advantage the Platypus has over the Autoflow.

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 Ultra, which is one of the fastest systems, takes 90 seconds per liter. If you do the math, it 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.

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Water flowing from the dirty bag of the GravityWorks with Clyde Minaret in the background. It takes 4 min 50 seconds for this system to filter an entire gallon, which is faster than all of the pump systems, and even the SteriPen for this volume.


Including the storage bag, the 4L system weighs 12 ounces, which is one of the lightest filters we tested, being beaten only by the Katadyn Gravity Camp, chemical treatments 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.

Differences in the 4L and 2L Systems

Both the two and four-liter 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 for you so you can better decide which one will work best for you.

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The 2L system set up with the 4L bag on the right for comparison.

2L System:
  • comes in Complete Kit ($110) or Bottle Kit ($100) options
  • can be used in three configurations: direct to water bottle, direct to a hydration bladder (without removing it from your pack) and direct to its own system (Complete Kit only).
  • 4-liter capacity
  • weighs 11.5 ounces for Complete Kit with bottle adapters and 9.5 ounces for Bottle Kit without second bag
  • hose attaches to clean bag water bottle cap with a rubber suction cup
  • clean bag is a Platypus soft bottle (can stand up on its own)
  • filter hose attachment is on the side of the dirty bag, and and sticks out slightly
  • includes water bottle adapter for push/pull bottle caps
  • also includes wide-mouth bottle adapter

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The suction cup push/pull cap adapter that comes with the 2L GravityWorks system.

4L System:
  • $120
  • 8-liter capacity
  • weighs 12 ounces
  • hose screws onto an opening in the clean bag
  • filter hose attachment is on the center of the dirty bag, and out of the way
  • no water bottle adapter

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2L vs. 4L reservoir systems. The 2L package allows for a total of 4 liters of water storage, and the 4L package can hold 8 liters of water. Notice the different locations of the hose attachments.

Best Applications

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.
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The GravityWorks (Platypus) and the AutoFlow (MSR) are neck and neck in our scoring but Platypus has inched ahead.


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.

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All it takes for this filter to work is for the dirty bag to be elevated over the clean bag. This can consist of sitting on a rock, hanging from a tree, or even just holding up the bag.


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.

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Scooping out water to treat with the GravityWorks.

Other Versions

You can purchase this versatile filter in either two or four-liter 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
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  • Create your own system using your own bottle or reservoir
  • Cost - $100 ($20 less than GravityWorks)
  • Weight - 7.2oz - 9.5oz (depends on configuration)
  • Flow rate - 1.5 Liters per minute (.25 less than GravityWorks)
  • Ideal for 1 - 4 people

GravityWorks 4.0L Reservoir Kit
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  • Replace worn-out or damaged reservoirs
  • Cost - $55
  • Kit includes: 4.0L Dirty Reservoir with Quick Disconnect and 4.0L Clean Reservoir

GravityWorks 2.0L Replacement Hose Kit
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  • Cost - $18
  • Comes with a clean and dirty hose, as well as a replacement fitting and shutoff clamp
  • Available for the 4 Liter version

GravityWorks Carbon Element
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  • Cost - $13
  • Helps to remove odors, flavors, and various other compounds
  • Approximate filter life - 1500 L

GravityWorks Universal Bottle Adapter
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  • Cost - $13
  • Filter directly into various bottles or hydration systems
  • Eliminates the need for a dedicated clean water reservoir
Jessica Haist

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OutdoorGearLab Member Reviews

Most recent review: August 28, 2016
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   Aug 28, 2016 - 02:43pm
matchthehatch · Fisherman
I brought the 4-liter GravityWorks with me and my group out to Yellowstone for a week of hiking and fishing. It's a great product. It filters quickly, is easy to use and fill, sure it doesn't filter viruses but that's not a requirement for most filtering in the US. However, I gave this 3 stars because of the design of the dirty water bag, which I now see (on Amazon's review page) is problematic for other people too (see below).

Be sure to follow the instructions and backfill through the filter, it speeds up the filtering tremendously. I like how the instructions are included on a tag in the mesh bag Platypus supplies for carrying everything. From time to time our 'clean' bag would fill up with water and a lot of air, not sure if we missed something in setting up the filter or if the air was already in the clean bag when we connected it — try to eliminate the air from the clean bag before filtering, or, alternatively, click the plastic shut-off device on the tubing after the clean bag has filled a bit, unscrew the clean-bag's cap, push the air out, close the cap, and restart the flow. Easy.

I had some trouble getting the filter to work one morning, a problem which was likely due to the temperature during the night: My friend's hat, which he had left out all night, was covered with frost in the morning, so it seems likely that some water in the filter had froze. I sucked air and water through the filter in an attempt to get it going and that got me a trickle of filtered water, which in turn must have defrosted the rest of the filter. As the outdoorgearlab review says, perhaps it's better to take the filter into your tent at night if you're expecting the temperature to be freezing or below.

However, I had to return it at the end of the trip because the supporting grommet came out on one of the holes that the nylon handle loops through on the dirty water bag. I couldn't get it re-seated, which meant that every time I hung the dirty water bag up, I was concerned that the side of the bag would tear from the weight of the water — and as this works by gravity, the dirty bag needs to be above the clean bag. Our plan B was to duct tape the sh*t out of the hole to make it last, but you shouldn't have to do this with a product that costs over $100. We also could have filled it with less water each time, I suppose.

Anyway, I haven't bought another one to replace it. I'd still recommend this to a friend (NOPE, see edit at the bottom), but with the reservation that perhaps Platypus should redesign the dirty water bag to eliminate this possibility. Personally I'm thinking of going with the MSR filter and bag — it doesn't appear to use holes in the bag to support the strap — and seeing if I can attach a different 4-liter bag to it.

EDIT, after reading a few reviews on Amazon I can see that other people have had the same or similar problems with the grommets on the Platypus dirty water bag, so I can't recommend this system until Cascade Designs changes the design of the bag. Oddly enough they also responsible for MSR so I would have thought they'd field test this more thoroughly.

Bottom Line: No, I would not recommend this product to a friend.
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