GravityWorks 4L System

This is AWESOME for groups. We do a family backpacking trip to a lake in Yosemite every year or two - and we can have more than 15 people there at a time. This means we have had to take turns pumping and sharing just 2 or 3 filters and it takes FOREVER. This sweet setup takes hardly any time... just scoop up some water and filter away. I think this would be helpful even with 2 people since it's super quick and then you'd be able to fill your water bottles and have water for cooking. It's also nice because you can store water in the clean water bag and refill as needed.LIMITATIONS: You definitely need something to hang them from (trees work great). You also need a source of water where you can scoop out a bucketful of non-nasty water. And be sure to read the directions about reversing flow just a little each time to un-jam it since particles build up more quickly than when you're pumping.Super easy and user friendly. I just wish we had gotten one sooner!!!

Used it for a 4 day backpacking trip in the High Sierras and it worked like a charm. Very easy to use and light weight. I wish the little pouch it came with was a little larger. Packing it back into the carrying pouch was a bit of a pain, but other than that it was a breeze to set up and use. We had 11 in our group and it took care of all our filtering needs. So simple to fill the dirty bag with water, hang it from a tree and let it filter water into the clean bag without having to pump and pump and pump. It is surprisingly quick as well. I think the system was the best camp gadget we had on the trip. Everyone loved it. Even the "proud" guys that were set up with techy filter systems of their own admired this setup. I have no need for any other filtration system after experiencing this.

This filter system works pretty darn good. I took it on a 3 night backpack trip on the Escalante River in Southern Utah with 6 people. We filtered between 30 and 40 liters for the trip.The filter started getting real slow by the last night and I was worried it was about done, for its useful life, which seemed pretty abysmal. Southern Utah typically has silty water, but the early spring runoff water we gathered appeared very clear, so I was quite surprised that it was going so slow with such little use. It even seemed to have stopped flowing. Tried back flushing while squeezing the clean water bag to increase the pressure going back through the filter. It helped, but not as much as I’d hoped. I always back flushed a little water as the instructions say to do, which I guess is mostly to get the air out of the filter so it will flow quicker. This is also supposed to clean the filter, but seems pretty pointless when you’re running the same water back through the filter again into the clean bag. When I got home I did a proper back flush, running a few liters of clean water back through the filter and discarding. This is really what is needed out on the trail as well. The first bit of water from the back flush was a little dirty, so even though the river water looked clear, there obviously was some bad stuff in it. After that back flush, the filter performed stellar again, taking 3 minutes to run 4 liters of clean tap water through it. Next time I’ll do a proper back flush on the trail when it starts slowing down, or back flushing a little onto the ground each time when filtering. It's easy to do.The conclusion: I love this filter system. I always hated pumping while trying to keep the intake hose out of the muck and sand, and getting very bored and worn in the process. There’s no waiting for dinner any more, and filtering while hiking is a quick process. I used to carry a ton of water, but we all only carried a one liter bottle, and stopped to refill if needed, which we did once during the day and called it a rest stop. The temperatures were cool, so in hotter weather it might be necessary to stop more than once, or carry a second bottle. In any case, I’ll never carry a gallon of water again, unless there is no water along the way, which does happen sometimes. We always check the maps for sources of water before heading out.Other reviewers have suggested or warned that you should carry a second filter system in case this one plugs up. I took a second filter cartridge, which is a lot lighter than a whole second filter system, but that shouldn't even be needed with proper back flushing. I didn't need to use that second filter.Filtering water is now a non-issue. The hardest part is walking from camp to the water and back again. It’s hard to complain much about that.

Incredibly handy! Before buying this I did an exhaustive amount of research on water filters. What sold me on this is the fact that you can get a lot of water in one shot, it filters FAST, and most importantly... NO PUMPING! If you're backpacking this is a no brainer. Water weighs 8.3lb per gallon and an adult needs about a gallon a day, so bringing water on a multi-day trip is not an option. This weighs less than a pound at 13.6oz! This can also save you money in the long run. The filter lasts for 1500 liters or 396 Gallons, If you're buying gallons of water from the store that'll cost you $350-$400. Even if you're filling from the tap this will save space and save you from having to lug water around.The other "straw" filters are handy, but if you need to fill a Camelbak bladder or use water for cooking, then you'll need a filter that is capable of filtering more water. The tubing and the storage bags are high quality and will not kink or deform. The hoses are long so you can hang the dirty bag from a branch and put the clean bag on the ground for maximum filtering speed, or you can just hang the clean bag from a lower branch. To dispense you can just detach the hose on the clean side of the filter and hang the clean bag as show in the picture.Want to get the most out of one trip to the water source? You can actually get 8 liters in one shot! Just fill the dirty bag and wait a short 3 minutes for it to filter. Then detach the clean water bag from the hose and screw on the provided screw cap to close the clean bag. Then will up the dirty bag and boom you've got 4 liters ready to go and another 4 that can be quickly filtered! That's 2.1 Gallons in one trip!Cleaning:Every 8 liters or so (depending on water quality) when the dirty bag is nearly finished filtering, simply lift the clean bag higher and back-flush it for about 5 seconds and then clamp the hose and discard the water in the dirty bag. For long term cleaning add 2 liters of clean water to the dirty bag, add a couple drops of bleach, and filter it through. You can towel dry the dirty bag, but the clean bag you'll need to just hang it for a few days in a dry place. The filter can be dried out by removing the bumpers and the plastic end pieces, and leaving it sit for a week.Cons:The filter is advanced but delicate, it cannot be dropped or used if the temperature may drop below 32F (0C) as it will damage the filter. You can easily test the integrity of the filter though by trying to blow air backwards through it. If there are bubbles on the other side, then the filter is broken, if not then you are good.I simply love this filter and couldn't be happier with my purchase. I hope you found this review helpful!