Platypus  GravityWorks Water Filter System - 4 L

This is my second GravityWorks Filter -- my first lasted me more than 10 years! Only needed to replace it because I was way over the recommended number of liters for the filter and my bags were starting to wear thin. I've tried so many other filters -- the pumps, the squeeze, etc, and this is by far the easiest to use and fastest way to filter. It's also super reliable. Unlike others, this filter has never failed me on a long backpacking trip! My wife and I do a lot of backpacking and it's so nice to get to camp, fill the dirty water bag, and let gravity do the rest. Instead of pumping or squeezing, you can just walk away and attend to other camp duties. This allows us to set up and break down camp much faster to get back on the trail. Easy to use and easy to back-flush if it clogs. The 4L size is perfect for 2-4 people. Water tastes great, too!

Used this at a camp out where I saw probably 8 other systems also being used, including pumps, squeeze bags, gravity bags without a clean bag, etc. Everyone left the camp out planning to buy one of these because you just fill the dirty, get them hanging appropriately, and come back after you e done some other tasks, and you have a bunch of clean water. No hard pumping or squeezing or anything else. Great system!!!

I've been using a 6L Platypus for several years now. They work extremely well and are easy to use. Overall it's probably a five star product. I'm rating it at four stars because of the following: They filter really quickly when new. But with several days of use, they slow down. And yes, I back flush each time I run a bag through. And if the filters freeze, they are totally dead. As soon as temps dip below freezing, you have to keep the filter in your shirt or pants. Lastly, the filters are just way way too expensive. $80 per filter. And they just seem to keep increasing in price. You can get the entire 4L bag system with filter for $100. So something is just off with this. It's almost enough to make me just use something else.

PROS *good for passively replenishing the group water supply at base camp. *The dirty water reservoir has a wide easy to fill opening with a slider closure. CONS *Clean reservoir is nearly impossible to dry out for storage (a week of daily shaking and trying to keep bladder from sticking to itself). I imagine they designed the clean reservoir so you wouldn't accidentally fill with dirty water, but it would be nice to have a slider opening on the clean reservoir (The dirty reservoir was easy to clean.)

It is a great filter with proper care. I use this for backpacking as well as for touring and living the camp life. I use it to fill mt 7 gallon eater container and it goes pretty quick once you get the "hang' of it. ;) Only downside, my clean bag had a strong plastic odor/taste, I have cleaned it with baking soda and it has improved but still has a faint taste. I do have faith that the clean bag will become neutral eventually but note that it does require cleaning prior to use...

I’ve used this system for 7 years, for between 3 and 5 people. It works perfectly. 2 things w.r.t. other reviews. 1) it isn’t necessary to get the clean reservoir completely dry because the pre-storage treatment uses chlorine. Therefore the remaining water will have enough chlorine in it to prevent virus or bacteria growth. It doesn’t matter if water is left behind. 2) I have been using water filters since the first one (Sweetwater) came out in the early 90’s. Pre-filters extend the life of the filters, but they will always need replacement after a while. That was the case then and it is the case now. Platypus sells new filters. They aren’t cheap but they’re a lot cheaper than a new full kit. Filters get slower over time and eventually get so slow that it’s worth replacing them, but they don’t just stop up, which would be very bad. So I feel that those reviewers who expect the filters to last forever need to recalibrate their expectations. Remember how iodine treatment used to taste? Vance

Went kayaking down the Colorado River from the Glenn Canyon Dam, down through the Grand Canyon. It was a group of 10 people with various gear, and only one other person had brought a water filter. I was able to filter all of the group's water during the trip, and having this system was so nice. The wide openings for the dirty bag made collection easy, and I never had any issues backflushing. Also, the set-it-and-forget-it with a fast flow rate worked out perfectly for the group. I will definitely be using this system whenever I am with large groups!

Have used this filter on 2 different trips with a total of about 8-10 filtrations and have backwashed at least 3-4 times. After the first trip I was having flow issues while trying to clean it for storage. On the most recent trip the flow was still very slow and even stopping completely. Luckily a fellow traveler allowed me to use their pump filter. Even now that I’m home and trying to clean it, I press on the quick-connect on the dirty bag and nothing comes out. I hook up the hose not attached to the filter to check if there is flow, and nothing comes out. I have felt around the openings of the quick connect and nothing seems to be blocking it on either side.

I have used this system for 8 years. There are very few outdoor water source that will not plug this filter after about 100 liters. Yes, I know how to backflush the filter to clean it. The only solution was to insert the MSR silt stopper filter between the dirty bag and the main filter this worked great. I could change the cheap silt stopper cartridge and make the more expensive platypus filter last a long time. Unfortunately it's impossible to find the MSR silt stopper replacement filters. So, after a one last frustrating group trip where I burned through 2 filters and barely eked out enough water keep the group hydrated -- the platypus system is gone. I can't find another inline pre-filter like the MSR silt stopper, so I'm going to have to find a different system entirely.

I like this because I can just hang a bunch of water on a tree limb and come back later to fresh and clean. No hunching over and pumping. The only problem I had is after the filter sat for a year it failed to drip water through no matter how long I tried. So unfortunately it looks like the filters have a weakness that over time they degrade and fail but I’m sure thats expected after a year or two.