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Owner Review Platypus Gravityworks 4L Water Filter - Anna Macquarie

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  • Anna
    Dear editors, Here is my review. Thank you! http://tinyurl.com/kdtyw6v Platypus GravityWorks 4L Water Filter Owner Review by Anna Macquarie October 15, 2013
    Message 1 of 1 , Nov 9, 2013
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      Dear editors,

      Here is my review. Thank you!


      Platypus GravityWorks 4L Water Filter

      Owner Review by Anna Macquarie
      October 15, 2013

      Reviewer's Information

      Name: Anna Macquarie
      Age: 24
      Gender: Female
      Height: 5 ft 9 in (175 cm)
      Weight: 140 lb (64 kg)
      Email address: annamacq AT sbcglobal DOT net
      City: Salt Lake City
      State: Utah
      Country: United States of America

      Hiking Biography
      Most of my hiking has been done in the western United States or in the Andes Mountains of South America. I am not a light weight backpacker - I carry a 50-60 lb backpack (22-27 kg). I cook two meals a day on a stove, and eat one meal a day of packaged items like dried meat and crackers. My cooked meals are simple, but are not freeze-dried. For breakfast, I eat oatmeal with dried milk and coffee, and for dinner, pasta or rice with sauce. I hike between 8-12 miles (13-19 km) a day, and sleep in a tent.

      Product Information
      Manufacturer: Platypus Hydration
      Website: www.cascadedesigns.com
      Product: GravityWorks 4L water filter
      Effective against protozoa: Yes
      Effective against bacteria: Yes
      Effective against viruses: No
      Effective against particulate: Yes
      Effective against chemicals/toxins: No
      Capacity: 4 liters
      Listed weight: 10.75 oz (305.75 g)
      Actual weight:11 oz (311.85 g)
      Width: 3 in (8 cm)
      Actual Width: 3 in (8 cm)
      Length: 9.5 in (24 cm)
      Actual Length: 9.5 in (24 cm)
      Filter media: Hollow Fiber
      Filter pore size: .2 microns
      Flow (L/min): 1.75 liters per min
      Cartridge life: 1500 liters
      Field cleanable: Yes
      Water Bottle Adapter: No
      MSRP: $119.00

      Features obtained from manufacturers website

      Product Description

      The Platypus Gravityworks 4L water filter is a duel reservoir water filtration system. It has a total capacity of 8 liters of water - it can hold 4 liters in the upper reservoir and 4 liters in the lower reservoir. The upper reservoir has a rectangular top and is rounded at the bottom. It is made of thick clear plastic, and feels light but sturdy. It is clearly labeled "DIRTY" in large bold letters on the right side of the bag to indicate that it is to hold the unpurified water. The top of the bag has a plastic zipper seal like a thick zip-lock bag. It has a black ribbon attached to the top edges of the bag to allow the user to hang the bag while it filters. It also has markings at intervals of 1 liter so that the amount of water remaining in the upper reservoir can be measured at any time during the filtering process. The bottom of the upper reservoir has a clip where the tube to the lower reservoir attaches.

      The tube is a clear plastic tube, with a grey plastic attaching mechanism at the top, the filter itself in the middle, and a screw top at the bottom where it attaches to the lower reservoir. The top of the tube has a round nose of hard grey plastic with a notch. It is inserted into the hollow opening of the upper reservoir and clicks into place. To release the attachment, the user pushes firmly on a grey button and pulls the tube out from the bag. As soon as the tube is attached to the upper reservoir, water starts flowing through the tube. The filter is made from Hollow Filter Membrane, and has a flow life of around 1500 liters, depending on water conditions, according to the manufacturer's specifications. The outside of the filter has an arrow indicating the direction of the flow. Below the filter on the tube is a clip which allows the filtering to be stopped at any time. This clip pinches the tube and locks into place, not allowing any water to pass. The bottom of the tube has a clear plastic cap that screws onto the lower reservoir.

      The lower reservoir is shaped like the upper one, but without the zippered top. It is made from the same clear plastic material, but is marked "CLEAN" to distinguish it as the bag for filtered water. It also has the markings at intervals of 1 liter, and has a black ribbon by which to hang it. Its only opening is a small round mouth where the bottom of the tube screws onto it. The filter comes in a black mesh bag, which holds all of the separate parts. The two bags can be detached from the tube and rolled up for storage in the bag, although the manufacturer recommends that the tube remains attached to the bags during storage to prevent cross contamination.

      Field Data

      The first time I used this filter was working on a backcountry trail crew in the Mount Rose Wilderness of northern Nevada. We had two filters to provide water for a 10-person crew. The filters were used over a period of three months. There were a total of six sessions of use, each 8 days in length. The filters were used at elevations between 8,000 and 10,000 ft (2,400-3000 m) in forested backcountry terrain. Daytime temperatures ranged from 50-90 F (10-32 C), with night time temperatures between 30-50 F (-1-10 C). The weather conditions ranged from snow to rain to sun.

      Since then, I have purchased my own Platypus Gravityworks 4L water filter, and have used it on four separate backpacking trips in Grand Teton National Park in Wyoming, Zion National Park in Utah, Grand Canyon National Park in Arizona, and the High Uintas Wilderness in Utah. On these trips, it was used at elevations of 7,000-9,000 ft (2100-2700 m), 4,000-6,000 ft (1200-1800 m), 2,000-3,000 ft (600-900 m), and 8,000-10,000 ft (2400-3000 m), respectively. The temperatures on these four trips ranged from 30 F (-1C) in Grand Teton National Park to 103 F (39 C) in the Grand Canyon. The terrain varied substantially, from exposed campsites above tree line in the High Uintas, to sand bars along the banks of the Colorado River in the Grand Canyon, to forested snow camping in the Tetons, to deep slot canyons in Zion. The filter was used for two days in Grand Teton National Park, five days in Zion National Park, sixteen days in Grand Canyon National Park, and three days in the High Uintas Wilderness.


      Overall, I am very pleased with the performance of this filter. The design is simple and effective. The gravity system is easy and requires very little effort on the part of the user. No pumping is necessary - the user only needs to fill the upper reservoir, find a place to hang it, and let gravity do the rest. In most terrain, finding a place to hang the filter is easy - any tree branch will be sufficient. However, I found that while camping in canyon country where there aren't many trees, it was sometimes difficult to find a place to hang the filter. Several times I had to result to holding my arm up while the filter drained since there was nothing in the area to hang it on. This was fine when the filter was new and drained quickly, but when the filter started to slow down after a few uses, holding a 4 liter bag of water above my head got very tiring and annoying.

      I found that this system filters large amounts of water very quickly. Two of these filters easily provided enough water for 10 people, each consuming 4-6 liters of water a day. However, under this high volume of use, the filters quickly lose their efficiency. When first purchased, they filter 4 liters of water in 2.5 minutes, as the manufacturer advertises. But after two eight day trips of filtering water for ten people, the filters took almost 15 minutes to filter the same amount of water. After four eight day trips, the filters were so slow that they were unusable, and had to be replaced. Additionally, the quality of water being filtered significantly effects the efficiency of the filters. When I first used the filters with the trail crew in the Mount Rose Wilderness, our only water source was a raging stream of snow melt that was brown with sediment. With this water the filters needed to be back flushed after every use to remain usable. This process was tedious, and made the filtering much less efficient. But since that trip, I have always used the filter on clear water, and the filter has been much more efficient.

      A major benefit to this system is the ability to store water as well as to filter it. I found that when using the system as an individual in the backcountry, I was able to camp farther away from water sources than I would have been able to with a different filter, because I could store eight liters of water in the system at a time. I was able to filter at the water source, fill up all of my water bottles, then fill up all eight liters of the system and take it back to my campsite. This would easily be enough water for all of the evening's cooking and cleaning, and I wouldn't have to visit the water source again.

      One part of the equipment that consistently stopped working on all three filters that I used (the two filters for the trail crew, and my personal filter) was the zip lock at the top of the dirty bag. This is a lock made from several teeth of very thick plastic. Even initially, it requires some effort to force the teeth to lock together - the user needs to push very firmly and slide her fingers along the seal with constant firm pressure. After a few uses, the pressure needed to seal the compartment became greater and greater, and finally, I was unable to seal the bag at all. Although it is annoying to not be able to properly close the bag, the filtration system still works fine when the top of the bag is open. I imagine that this might compromise some of the sanitation of the system since the top is open to the elements and has a risk of obtaining large debris, but I was never personally very bothered by the top of the bag being open, since it was the bag containing the unfiltered water.

      Another part of the system that became more difficult to use after time was the clip that attached the tube to the upper reservoir. After the heavy use of the filter on the trail crew, it became very difficult to detach the clip, and eventually, I could not detach it at all. Like the problem with the zipper, this was slightly annoying, but not something that compromised the sanitation of the system. Once the clip no longer detached, I had to take the entire system to the water source to fill the upper reservoir instead of just taking the dirty bag as I had previously.

      The system packs up and stores very well. It is light weight, and since it is made of flexible plastic, it is easy to mold into any part of a backpack. The black mesh storage bag is small enough to contain all of the components in an efficient way, but is large enough that it is easy to pack up the entire system into the bag.

      My final remark on the system is that I found it difficult to dry out between uses. The manufacturer recommends using a bleach solution to sanitize the bag when you return from a trip. I have done this after every use, and the rinsing process is not difficult. However, completely drying the reservoirs is very difficult. After the sanitation rinse, I hang the bags and try to use clothes pins to open them as much as possible to allow for air flow. But the sides of the bags naturally want to stick together, and even after weeks of hanging, I am never able to rid the bags completely of water droplets. So far, this has not caused any problems of mold or bad taste, but it bothers me to put the bags away while they are still wet, and I imagine that over time this could cause problems.

      Pros and Cons

      • Requires minimal effort to use
      • Capable of storing large amounts of water
      • Great for supplying water for large groups
      • Efficient
      • Light weight
      • Flexible

      • Requires a tree branch for hanging
      • Zippered top quickly becomes unusable
      • Loses efficiency over time
      • Difficult to dry
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