Gravity Water Filter

Usually when I go hiking I take along my portable Katadyn Guide water pump and use it to fill up one or two 2-liter Platypus bags for later drinking. While the Katadyn works extremely well and I’ve never experienced any problems resulting from the water I’ve pumped and later consumed, I’ve noticed that it is by far one of the heaviest pieces of gear that I carry when backpacking. My friend Andy has the Katadyn Hiker version which is more compact and equally as reliable, but still on the heavy side. I wanted a better, lighter solution.

Recently I’ve been taking along my home-made portable gravity water filtration system based on the one designed by Jason Klass. It uses an inexpensive Aquamira Frontier Pro water filter, Micropur water purification tablets, some tubing, and two Platypus 2-liter bags. Even combined it’s very light weight and has the advantage of being flexible enough to be used in different ways other than just for a gravity filter – for example I can use the clean bag and the tube as my hydration pack, or I can use the Aquamira and the bite valve to drink directly from a stream or water bottle of dirty water – the gravity filter is just an easy way to go UL and let the water’s own weight do the work for me while I go off and do other things. Below is a picture of the basic setup that I used during a backpacking trip this past weekend.


There are two Platypus bags used for this, one for dirty water (from the lake, creek, stream, wherever) and one for clean water. It’s very important that you clearly mark which bag (and cap) is for the dirty water so that you never use them the wrong way round. You should be able to see some large XXXs marked on the top (dirty) bag in the picture, the lid also has a large X on it. Once the dirty bag has been filled with water from the creek or stream, drop in two (one for every liter) Micropur water purification tablets and wait 20 – 30 mins. The Aquamira filter will filter out all of the nasty stuff down to 2 microns [edit: 3 microns], but just to be safe the Micropur tablets will kill all of the smaller stuff that’s lurking around in the water.

The Aquamira is designed to screw directly onto a standard bottle sized opening and fits snuggly onto the Platypus (dirty) bag. I remove the bite valve that comes as standard on the Aquamira filter and use the plastic tubing from my hydration pack (minus the bite valve is uses) to connect from the Aquamira to the second (clean) Platypus bag. The dirty bag has a little Kelty Triptease cord ties to it so that is can be hanged from a branch or notch. Now all that is left is to hand the dirty bag and wait for gravity to do the work. It took just under 14 minutes for all two liters of water to pass through the filter, which as it turned out was barely enough time to go throw the ball for Coco a few times :)

The result was two liters of crystal clear ice-cold refreshing water that had no taste of the purification tablets. There are many commercial gravity water filtration systems out there, including the Platypus one I blogged about recently, but most are expensive and use filters that cost almost as much as the whole device to replace. The system that Jason has devised and that I now use is cheap (~$40) and uses the Aquamira Frontier Pro as the workhorse which is good for 50 gallons of filtering and costs $20 to replace, other than the Micropur tablets, the other components should last a very long time if taken care of.

It’s very satisfying to come up with a better solution to an old problem. Even though this was dreamed up by Jason, I’m very pleased with how I’ve put mine together and how it has turned out to be a first class gravity filtration system. I hope you find this useful and be sure to check out Jason’s video.

The Great Sleeping Pad Dilema

Hiking with Coco