I’ve heard it said that gravity is the force that unites all outdoorsmen: when it comes to backpacking, all of us fight its effects as we carry increasingly light gear, and all of us feel the soreness in our knees when we carry our load back down all of the elevation we earned.  Cascade Designs’ release of their Platypus GravityWorks Water Filter takes us a step further in exploiting gravity to do some productive work for us – namely, filtering water while we kick back and relax.

Platypus GravityWorks Specifications:

  • Filter Pore Size: .2 Microns
  • Effective against Protozoa, Bacteria and particulate matter
  • Weight (complete kit): 11.05oz.
  • Cartridge Life: 1500L
  • Filtration rate: 1.5L/minute
  • MSRP: $120


Platypus GravityWorks Filters for You

My time testing the GravityWorks filter has definitely been eye-opening.  First off, let’s examine some of the preconceptions that the concerned backpacker might hold regarding the GravityWorks.  Personally, I expected slow filtration, a bulky system and easy clogging; none of these things are exactly what I want to see in my filters, so when Cascade Designs sent along the GravityWorks with the promise “you’ll never want to pump again,” I was skeptical at best – sometimes it’s nice to be wrong.

First of all, let’s start with the simplest categories of all, weight and price.  The GravityWorks slots in at 11.05oz for the complete kit (including a Platypus bottle and several adapters).  Obviously, that’s going to be blown out of the water by UV pens that can weigh less than 3oz, but that’s a poor comparison. Comparable filters include the MSR Sweetwater at 11oz, the Katadyn Hiker Pro (my old pump) at 11oz, and the First Need XL from General Ecology at 160z.  As far as price goes, the GravityWorks is by far the most expensive at $120 MSRP, though the First Need XL (whose .1 micron filter is effective against viruses) goes for $118 according to their website.  Clearly, we’re paying for the novelty of the GravityWorks, though we’ll have to see how well that cost is recouped by performance.

Clearly labeled 'Dirty' bag makes it harder to screw up and get Giardia

Clearly labeled ‘Dirty’ bag makes it harder to screw up and get Giardia

At its heart, the GravityWorks is a very simple contraption.  There are two bags, two hoses, some adapters and one Hollow Fiber filter and with these components you can strain most of the bacteria and protozoa from a water source; this simple description doesn’t give due credit to Cascade Designs’ fantastic engineering and thoughtful additions.  When you first unpack the filter from its 7.5 inch zip case, you’ll notice that the Clean and Dirty bottles are clearly labeled and idiot-proof.  I say idiot-proof lightly, but simplicity is a beautiful thing if it’s dark and you’re tired and thirsty.

The dirty bag has a special quick-release valve that won’t leak when it’s unhooked from the system, so you can scoop up water through the proprietary Platy Zip opening in the dirty bag with no fear of getting your clean hoses in the stream.  From there, clamp down the tubing with the included clamp and hook up your dirty water to the system.  At this point, gravity is going to do all of your work – just hold the dirty bag above the filter and unclamp that sucker to let the good times roll.  It’s helpful to hold the filter above the dirty bag for just a moment after the initial flow so that you can get rid of bubbles (or purge the air, to be proper) and get a fast laminar flow.

Bubbly flow like this will flow down your filter rate - even if it's pretty.

Bubbly flow like this, though fun to watch, will slow down your filter rate.

At this point, you’re probably staring in awe at how fast the water is draining out of that dirty bag.  Guys, it goes fast.  If Cancellara were a filter, he would probably be some other filter since Fab isn’t quite flashy enough.  However, if Peter Sagan were a filter, he would definitely be the GravityWorks because he’s fast and does the job in style.  By the way, the pump’s 1.5L/min stacks up really well against the majority of filters on the market.  The MSR Sweetwater pumps out 1.25L/min and the Katadyn Hiker Pro does 1L/min, while something like the Camelbak All-Clear UV filter does a lackluster .75L/min.  That’s really darn fast, making the GravityWorks ideal for basecamp or groups (or, heck, any other time you need to filter water).  Platypus even includes a strap to hang the bag from a tree or an exasperating Boy Scout who needs a job.

I never had any problems with the filter speed slowing down or clogging, but I also take my water from sources that most backpackers can only dream of.  There simply aren’t a whole lot of nasty, silty lakes or streams in Northern Nevada wilderness.  That being said, Platypus recommends backflushing the system (putting the clean bag as the highest point and letting it flush back through the filter) to restore flow rate.  Failing that, it’s time to take the filter home for a good clean-out with hot water and elbow grease.  Being a gravity filter, it’s obvious that you can’t force water through the system, so expect slowed performance in dirty water; frequent backflushing and carefully keeping the hoses devoid of air will mitigate this problem.  This brings up the other con of the GravityWorks’ design: it’s hard to get water out of shallow ponds that a pump filter could easily suck from.

Check out the quick-release port, nicely complimented by dead grass and dirt in the bladder.

Check out the quick-release port, nicely complimented by dead grass and dirt in the bladder.

Platypus took care to make hose and bag storage dead simple.  There’s a separate pocket in the storage pouch for the dirty reservoir, while all of the clean stuff wraps up tidily to fit in the large, mesh-backed zip pocket.  There are also basic instructions sewn into the storage kit.

The Good:

  • Boy oh boy oh boy, this thing filters fast in good water
  • Reasonably light, but not special
  • Intelligent hose management and storage
  • Clearly labeled bags

The Bad:

  • Pricey!  $120 could buy you two Katadyn Hiker filters at the right outlet store
  • Tends to slow in cloudy water
  • Bladder design makes it unfeasible to pull water out of small, silty ponds

The Bottom Line

Alright Platypus, you win this time – you’re right, the GravityWorks makes me never want to pump water again.  It’s just so simple and easy to walk away from this system and let it work.  It’s safe and effective, not to mention intuitive and convenient.  Travelers who have problems with gritty water may want to consider a traditional pumper, but for the vast majority of backcountry enthusiasts the GravityWorks is top dog of filtration.

Buy Now: Available at REI.com

About Author

Kevin Glover is an outdoorsman living, climbing and biking in Spokane, WA. Originally from the Nevada high desert, he moved to the PNW for its mild winters and allergen-free summers. He has guided throughout the Cascades and Enchantments for Peak 7 Adventures.

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