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Gravity feeds pure water to campers

Sun., Sept. 2, 2012

No pumping required as gravity filters water from bag to bag

Procuring clean water in the wilderness can be a pain. Pumps are hard work. Purifying tablets require a long wait. But on a recent trek in Northern California, I simply scooped some water from a stream and hung a bag in a tree.

The venue was the Lost Coast Trail, an ocean-hugging route where rivers pour out of green mountains and empty right into the sea. My water-purifying product of choice, the GravityWorks Filter from Platypus, gave our group near-instant access to drinkable water anywhere on the hike.

As its name says, the GravityWorks Filter counts on nature’s primal pull (gravity) to coax water through a filter, no pumping required. The product, a system of tubes, water bags, and a filter cartridge in the middle, lets you grab untreated water then wait for gravity to do the work.

To operate, fill the GravityWorks’ “dirty” reservoir bag with lake or river water. Hang that bag in a tree or simply hold it up. Water seeps out of a hose on the bottom, coursing a foot through rubber tubing before entering a filter.

Clean water flows out the other end, slipping through a hose and collecting in the unit’s “clean” reservoir bag, ready to drink.

The whole process takes just a couple minutes. There is very little effort required, allowing you to fill, hang the bag, and relax as water is dripping through from dirty to clean.

Platypus quotes a purifying speed of 1.75 liters per minute, which was about what we saw on the Lost Coast. The GravityWorks’ filter unit has a pore size of .2 microns. That’s enough to eliminate bacteria, protozoa, and other “bugs” that may taint fresh water. It is not effective against viruses, but for most wild places that is not a worry.

Online, the unit costs $110 at, and it is made in the United States. Platypus cites 1,500 liters as the life of the filter, which can be replaced.

In a backpack, the GravityWorks folds and packs up fairly small. Stack the bags together, coil the hoses, and slip the filter unit in between – you’ll have a 10-ounce purification system always at hand no matter where your trek may lead.  

The system is particularly useful for groups.

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