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Reviews > Water Treatment > Filters > Platypus GravityWorks Water Filter > Owner Review by Ray Estrella

Platypus Hydration GravityWorks Water Filter
By Raymond Estrella

August 28, 2012


NAME: Raymond Estrella
EMAIL: rayestrellaAThotmailDOTcom
AGE: 52
LOCATION: North Western Minnesota, USA
HEIGHT: 6' 3" (1.91 m)
WEIGHT: 225 lb (102.00 kg)

I've been backpacking for over 30 years, all over California, Minnesota, and many western states. I hike year-round in all weather, and average 500+ miles (800+ km) per year. I make a point of using lightweight gear, and smaller volume packs. Doubting I can ever be truly ultralight, I try to be as light as I can yet still be comfortable. I start early and hike hard so as to enjoy the afternoons exploring/chilling. I usually take a freestanding tent and enjoy hot evening meals. If not hiking solo I am usually with my brother-in-law Dave or my twin children.

The Product

Manufacturer: Cascade Designs Inc My new filter
Web site:
Product: GravityWorks water filter
Year manufactured: 2012
MSRP: US $109.95
Listed weight: 10.75 oz (305 g)
Actual total weight: 11 oz (312 g)
Storage sack weight: 1.1 oz (30 g)
Clean reservoir weight: 2.2 oz (62 g)
(In case it is used with smaller bottles.)
Dimensions listed: 3 x 10.75 in (7.6 x 27.3 cm)
Dimensions verified accurate

Quick & Dirty, Nitty Gritty

While not the most robust filter I have ever used, the Platypus Hydration GravityWorks is the easiest and fastest one I have ever owned. Putting out safe drinking water in well under a liter a minute the GravityWorks has become not only my main family filter but the one I take most often even on solo hikes. Its only hiccup comes when back-flushing, but that can be avoided by a little thought beforehand. Please read on for the details.

Product Description

All the parts

The Platypus Hydration GravityWorks water filter (hereafter referred to as the GravityWorks or filter) is lightweight pump-free filter aimed at both weight conscious backpackers and groups. A re-design of Platypus's first gravity filter, the CleanStream the company uses the Hollow Fiber technology first seen in the MSR HyperFlow filter.

The way the technology works is like this. Think of a sealed-at-one-end glass straw with a bunch of little holes in it. As water is pushed against the side of the straw anything bigger than the holes is trapped outside while everything else passes into the straw and out the other end. In the case of the GravityWorks there are thousands of straws with hundreds of thousands of 2-micron holes to stop the bad stuff like Giardia and cryptosporidium that can be found in backcountry water sources.

Rather than use a pump to force the water past the filter the GravityWorks uses gravity to do the work. A 4 L BigZip bag clearly marked Dirty holds the suspect water. The dirty water reservoir has a quick disconnect that matches up to a silicone tube that goes to the inlet end of the grey filter cartridge. Both reservoirs have a thin nylon strap that allows them to be hung from a tree branch or rock knob.
Packed up
At the outlet end filtered water goes through a clean tube to a clearly marked 4 L Clean reservoir. This one is reminiscent of the company's Hoser Hydration reservoirs in as much as it has just a small opening about the size of a pop bottle top. This will accept any type of Platypus cap or tube, and a clear Platy cap comes with the system.

A pressure clip on the clean tube allows the flow of water to be stopped at any time. The tubes end fits all Platypus containers so the GravityWorks can be used with any of their bottles or hydration systems should the big Clean reservoir be left behind to save weight.

A black drawstring with cord lock storage bag is provided to keep everything together. The bag is made of mesh on one side to facilitate drying. The whole works is not much bigger than a 1 L Nalgene bottle.

To clean the GravityWorks is pretty easy. Just fill the clean reservoir and then lift it above the dirty reservoir, while dropping the dirty reservoir down to ground level. If the dirty reservoir is allowed to run dry before lifting it above the clean one it will get air in the filter resulting in a horrible vapor-lock making it very difficult to back-flush. The trick is to do the reservoir position swap while there is still water flowing out of the dirty side of the filter. Now the water runs smooth and the pressure of the clean water back-flushes the cartridge, popping the stuff caught in the tiny holes back out and into the dirty reservoir. Now dump that water and the GravityWorks is ready to go again.

Field Data

Hanging at McCarty Lakes

I have used the Playpus GravityWorks on approximately a dozen two or three-day backpacking trips and two camping trips, all in Minnesota (MN). Locations have been along the Red River of the North near Hendrum and Halstad, Paul Bunyan, Two Inlets and Smokey Hills State Forests, Chippewa National Forest, Lake Bronson and Old Mill State Parks and on the Superior Hiking Trail along the Beaver River. Temperatures have ranged from lows of 34 F (1 C) to highs of 88 F (31 C) in conditions from sunny, hot and humid to stormy and raining. It has held clear eastern MN river water, not-so clear central MN lake water, and absolutely filthy western MN river water.

The picture above was taken at McCarty Lakes in Paul Bunyan State Forest and the one below was taken along the South Fork of Two Rivers in Lake Bronson State Park.

Good grief, I look like a CD ad...


I have to thank Cascade Designs for introducing me to gravity systems. April of 2009 I bought their first system, the CleanStream. After my first trip with it I was hooked as were the people I hiked with that I let use it to save time. I never got around to reviewing it as I spent over a year helping another author work on a huge water treatment article that saw me using 11 different systems. When I read that Platypus had done the redesign and lightened the system I decided to get the new GravityWorks and use the heck out of it. I am happy I did as I like it even better that the first model.

The best thing about the GravityWorks is the ease of use. No more sitting and pumping until my forearms ache to fill bottles. Just fill the dirty bag and go work on something else in camp while it filters. But I don't need to be gone very long as this thing is a speed demon. I have timed it at 40 and 45 seconds per liter in the field.

With the BigZip opening on the dirty reservoir filling is pretty easy. I just scoop up lake water or hold it under a running creek or river. Sometimes I have to use a separate water collection device like a collapsible bucket or the company's Water Tank (see review) as a settling container to allow dirt and debris to settle out first. This makes the filter last longer between back-flushing and I am sure extends the life of the cartridge which Platypus lists as 1501 liters. Really I don't know why it would not be more as long as it still can be back-flushed enough to get a good filtering flow once more.

At the Brown, I mean Red River

A good example of what the GravityWorks can do is seen above. The misnamed Red River of the North is a very dirty river that winds north through a lot of farm land. The predominately clay soil seems to all end up in its brown water. Even after settling in a bucket there is still a lot of dirt in suspension. Here is a picture I took of the dirty bag next to the clean bag after it was half filled.

Which do you want to drink?

My neighbor, a farmer who gave me access to his land to hike on, wanted to see what I could do with the river water, which is why I took that shot. He was amazed. I was amazed at what came out of my GravityWorks once I got home! ;-)

I love the weight of the GravityWorks. It is actually lighter than the small pump filter I used to use for most of my trips. I often leave the clean reservoir at home as I usually am using a Platypus Hoser and have one of their smaller bottles along for drink mixes too. As it fits all their products (and I use their products just about exclusively since 2005) I am set no matter what I have along. When I have the kids with me I do use the clean reservoir to have plenty of water on hand in camp. I did say it was easy to use right? Well it is child's play. The kids like filling their Platypus SoftBottles (see review) with the GravityWorks. They count how fast it fills. Here is a picture taken on the shore of the Beaver River on the Superior Hiking Trail. Raymond is filling his SoftBottle while Emma just washed hers off at the Water Tank. She dropped it in the dirt right as she finished.

Happy kids hydrating

The only thing I can suggest for improvement is to make the filter cartridges strong enough to allow back-flushing with a faucet adaptor. That would lengthen the life of the unit as it would get more of the clogged bad stuff back out of the filter holes. It would make back-flushing easier too as it would avoid the vapor-lock situation completely.

We are all pretty happy with the GravityWorks filter and I expect we will be grabbing it first for years to come. Well, unless they make a better one again.

This report was created with the Report Writer Version 1.5 Copyright 2012. All rights reserved.

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