The GravityWorks comes with a clearly labeled "clean" and "dirty" bag that each holds 4 liters for a storage capacity of 8 liters total. It comes in both a 4L and 2L size. If you seek a quick and easy to use filter where setup time and a few extra ounces isn't a big concern, consider this award winner. It filters quickly and easily. Best used for clear water sources and groups of one to many. It wins our Editors' Choice Award because it performs well all-around. It's fast, reliable, and offers deliciously clean water from the most disgusting sources.
This filtration system is easy to use and can turn gross water into drinkable water.
If you're seeking fresh, clean, water free of most water-borne pathogens, the Gravity Works 4L will meet your needs. Loaded with a hollow fiber filter with an absolute pore size of 0.2 microns, it'll filter out all bacteria and protozoan lifeforms including giardia and cryptosporidium. It does not filter out viruses so if you plan on traveling to countries where they might be an issue, consider a different option.
In our tests, we loaded this filter up with everything from clear to stinky, murky water. It does excellently when the water is clear and does get rid of smells. However, when testing it with high sediment (like all filters in our tests), it did clog easily after just 2L. As a result, this filter does best with clear water, or you will need a pre-filter. See the tip below.
A look at water quality after gathering from a turbid river.
If you're planning on visiting an area where your water source will likely contain substantial amounts of sediment (like the Colorado River), it's important to note that all filters will struggle. Make sure you pre-filter water that is brown or heavy with silt or sediment. Put it into a bag to allow it to settle (without disturbing it), then decant the clear water off the top, leaving the heavier sediment at the bottom.
Durability and Maintenance
This filter seems to be well-constructed and quite durable. The plastic overlay offers resistance to punctures and holes. When pulling at the seams, the welded plastic stayed intact and did not tear apart easily. The filter itself is a little fragile and requires care. The hollow fiber design can easily stow in its reservoir bags for a little extra cushion. Also, care should be taken to ensure that it is not frozen, which will damage the fine fibers inside.
In terms of maintenance, the filter is pretty easy to maintain. It has a lifespan of 1500 liters, and cleaning is super simple. If you notice that the flow begins to slow, flip it the other way, fill up the "clean" bag and allow 4L to flush it out. When finished, flip it back over.
The filter also has a natural way of telling you that it's no good anymore. When the backflush doesn't work, it means that the natural fibers inside are clogged with captured material, and it's time to buy a new filter. Overall, maintenance is way easier than taking the whole thing apart and scrubbing it clean. That said, if you're adventuring in a place with lots of sediment like the Colorado River, or anywhere in the desert for that matter, be sure to let the sediment settle out before filtering; if you don't, this will clog the filter, leaving you in a predicament that could be dangerous.
We see the solid connections here and the backflushing system above. When the filter gets clogged from lots of sediment (which it will), simply detach it and flip the filter to clear it of clogs.
The durability and construction of this product seem to be bomber. While we didn't experience any issues, we must note that online, a few users reported that the bag tore at the connection between the nylon clips when filled. We tried this over and over again to see if it would tear and didn't observe any problems.
It treats water very quickly once set up. We tested the rate of flow over three trial periods, and the GravityWorks proved to have one of the most consistent time trials, filtering one liter of water in a mere 52 seconds on average.
While this is a little slower than the advertised 1.75L/min, we are super happy to know that when the bag gets to a low volume, the flow rate is constant, where other gravity filters slowed way down. The convenient location of the outlet at the bottom of the bag sucks up every last drop of water. With this kind of output, it's perfect for use as a base camp filter. You can fill it with water, and have 4L filtered in just under 5 minutes! Both bags have an easy-to-use clip so they can hang. This feature allows you to access and pour water for a variety of uses. Fast, easy, convenient. No need to pump or suck.
Fast and convenient.
Weight and Packability
This is a lightweight setup that won't take up too much space in your backpack. Weighing 11.45 oz and taking up about as much room as a Nalgene bottle, it suits long backpacking missions where going ultralight isn't a huge concern.
Throw it in along with a bag of wine, and you'll be just fine hiking up the steeper trails. Of the gravity filters tested, it's one of the lightest and is comparatively lighter than the hand pumps we've tested. This weight takes into account the two bags (clean and dirty), hoses, filter, and the stuff sack into which it easily packs.
Ease of Setup
Advertised as a water filter that's perfect for larger groups, it's also an excellent option for the solo through hiker. While it's not as easy to set up as other filters that you can gather water on the go, of the gravity filters tested, the GravityWorks doesn't have many moving parts and is pretty easy to use. The only downside is that you have to be able to scoop up your water. So this filter isn't a great option if your water source is a shallow puddle. Lakes, rivers, streams and the like are just perfect.
Offering a two bag setup, it provides you with the option to store clean and dirty water on the go. If you know that you're going to encounter a section of trail without water, load up the "dirty" side as an auxiliary reservoir.
When you're ready to filter, find a place that you can hang or lay down the "clean" bladder that is a little higher than the filtered end. Unlike other gravity filters, you don't need a huge difference in height between the clean and dirty reservoir to allow filtration, which is due to the location of the outlet in the bottom right corner.
Gathering water typically requires a flowing source.
Attach the connection end into the "clean" reservoir, connect it to the filter, and connect that end to the dirty bladder. Make sure that the zip closures that can be difficult to zip in cold conditions are closed and get ready for filtration.
Find a tree branch or the like to suspend the bags from.
Ease of Filtration
Like all gravity filters, this part is super easy. There's no pumping or sucking required. Unclamp the hose and wait for beautiful, clean, fresh water. What's more, you don't have to use the "clean" reservoir provided. The adaptor on the end of the hose is pretty small and will easily fit into the neck of any bottle or the body of any hydration bladder. You just have to hold it in place.
This system will maintain a substantial rate of flow, even when it gets pretty empty. If hung up, it will shift under the weight of the water as it trickles to the corner, sipping up every last bit of water collected. Overall, filtering water with this setup is super easy. Once the clean reservoir is loaded up, there is a cap you can put on it to use as a storage reservoir. It can also be clipped up as a handwashing station or even a refreshing shower on a hot day.
Filtration with the Platypus Gravity doesn't require a huge height differential.
If you're planning on an extended backpacking trip and you don't want to work too hard to lots of water, then the Platypus Gravity Filter 4L is an awesome option. It does best in places with clean water where you can scoop up a bag at a time. While it's advertised for base camp use, it can easily be used with the solo thru-hiker or a duo of two if you have a little extra space in your pack.
We spot a rainbow after a big storm. Here we backpack into the remote areas of Peru. With a gravity filter in hand like the Platypus, it makes gathering water easy.
It can store up to 8L of water (with both reservoirs) and works well for clear water sources. Avoid using it in freezing temperatures as the water filter cannot withstand freezing. Also, if you need to get rid of viruses or gather water from shallow basin water sources, get a purifier. Overall, it's versatile, easy to use, has excellent flow and is stacked with a plethora of uses.
Retailing for $110, we think the value is right where it should be. The Katadyn Gravity Camp is about $20 less, but it doesn't perform as well as the Platypus. Plus, it should be the last gravity filter that you buy. Given that the filter cartridges will last you for about 1500 Nalgene bottle fills, and don't cost much to replace, it's a good deal.
The Platypus GravityWorks filter is our favorite for backcountry travel. It can filter a lot of water quickly, easy to set up, and requires no effort in the filtration process. It gets rid of all microorganisms but doesn't protect against viruses. While it functions quite well to get many people hydrated in a base-camp style, it is also super useful for the solo traveler who might have a little extra room in their pack. The best gravity filter out there, in our humble opinion.