This system is a 4 liter gravity feed water filter that consists of two water bags, one to fill with unfiltered water and a second to collect the filtered water. The key is to simply keep the clean bag lower than the unfiltered bag, and gravity takes care of the rest. The two bags are connected by a three-foot long hose and an in line filter. Both bags have built-in handles, which you can secure with the included Nite Ize S-Biner loop. The dirty bag has a screw on cap and the clean bag provides two methods for dispensing water – either by using the built-in spout with on/off valve or with the included drink tube and bite valve (not included). The filter can be field maintained or at home with the included faucet adapter. The pack weight of the system is 18 oz. and the filter itself has a million gallon guarantee by Sawyer. As far as filtration effectiveness, this system physically removes particles, protozoa, and bacteria down to 0.1 micron in size, including giardia, salmonella and cryptosporidia.
While my experience with this filter is limited at this point, my initial impression is very good. While camping just above Sandy Creek at Enchanted Rock Texas State Natural Area, this filter provided a constant supply of running water for two of us during an overnight trip. With the large four liter capacity, we didn’t feel like we needed to be ultra conservative with our water consumption. After filling the dirty bag with water from the creek we hung both the dirty bag and the clean bag from a tree limb, keeping the dirty bag a couple feet above the clean bag. This allowed for plenty of gravity-powered flow. The four liter bag was full in roughly five minutes and the filtered water tasted great. We were able to easily fill Nalgene bottles, fill pots for cooking, and rinse our hands with the spout on the clean bag. This worked great, it was like we had a camp faucet on our backpacking trip! The spout has a nice valve which allows you to control the flow of water. After we drained the first four liters, we headed down to the creek for another fill-up. This time, taking both bags to the creek, we decided to fill the dirty bag and filter immediately, and fill the dirty bag again before heading back to camp. Setting the dirty bag on a large rock provided a nice gravity-powered flow while filtering at the creek. By filtering 4 liters immediately at the creek and then refilling the dirty bag, this provided us with a whopping 8 liters of water (after the remaining 4 liters in the dirty bag were filtered later back at camp). This ended up being way more water than we needed, but I’d rather have more than I need than not enough when it comes to water.
Maintenance for the system is pretty simple. There was no need to backflush the system during this short trip, but if this was necessary, it can be done by pushing clean water back out of the clean water bag with the filter attached. Before storing the unit long-term, Sawyer recommends running a few capfuls of bleach and water through the dirty bag and filter.
Once I decided on a gravity filter, next I had to figure out which one to get. The Platypus GravityWorks filter interested me, especially because it’s a bit more affordable than the Sawyer system. In the end, there were several features the Sawyer 4l system had that the GravityWorks did not have, which helped make my decision easy. Most of this I’ve already mentioned, but to recap, I love the fact that both of the bags are made of sturdy nylon and have built-in handles. This makes it easy to hang the bags on a tree limb, line, or even your pack.
Also, since the dirty bag has a screw on cap, I don’t have to worry about the bag opening up on me unexpectedly. This is especially important if I need to put the full dirty bag in my pack.
The adjustable spout on the clean bag is a great feature, which proved to work just as well as I anticipated (again, like having your kitchen faucet with you).
The filtration ability of the system is impressive too - 0.1 micron level filtration is better than many competing systems, especially with Sawyer’s million gallon guarantee on the filter (might as well call it lifetime!).
Also, because of the large filter surface area, Sawyer claims this unit has a backflush requirement of 1:20 when comparing it to a traditional pump type filter, which means that for every 20 times a pump type filter needs to be backflushed, the Sawyer system will only need one backflush. I can’t speak to validity of this, but I haven’t noticed any flow reduction after filtering 12 liters of water. The included faucet hookup for backflushing is a nice addition too, which should make backflushing at home a breeze.
There are a couple potential drawbacks to the system that should be pointed out. At 18 oz. pack weight, it’s not the lightest filter on the market. This large 4 liter capacity would be great for a group of several backpackers and the weight could certainly be justified. If you’re going by yourself and are trying to stay ultralight, you may want to look at alternatives.
Another consideration is the size of the system. It wraps up reasonably small, but there are certainly smaller alternative water filtration/purification systems available. The water bags collapse to be flat, but with the screw-on cap, water spout, filter unit, and hose, it will occupy a bit of your precious cargo space.
Lastly, this isn’t unique to this Sawyer system since many filters are the same way, but it’s important not to let the filter freeze as this can damage the filter itself and impact its effectiveness. Some folks have suggested snuggling up with you filter in your sleeping bag at night to keep it warm if it’s expected to freeze.
All things considered the Sawyer Complete Water Treatment System – 4 liter has been a delight and is certainly Thrifty Gear recommended. It has a large capacity, impressive filtration capability, some great features, and effectively a lifetime filtration guarantee. I waited for my spring 20% member coupon to arrive from REI and ordered this online since it wasn’t available in my local store. The great thing about shopping at REI is of course their satisfaction guarantee. It’s nice to know that if I ever have any issues with this filter, I can simply pop in to my local store to get help. Plus, with the 20% off coupon, I couldn’t go wrong. I paid $109 ($136 less $27 with the coupon) plus tax. This wasn’t the cheapest gravity filter available, but with its features, I felt it provided the most bang for my buck.