Ultralight Water Filtration and Purification Kit

In my years of backpacking in the wilderness and traveling in countries with questionable water supplies, I've realized that clean water is a top priority. The kit below works as a miniaturized municipal water treatment facility that you can bring with you to developing countries with no infrastructure for clean water, disaster zones, or the wilderness.

In survival, there is something called the "Rule of Threes": make sure you have at least three ways of obtaining each of your survival needs. While normally this would conflict with ultralight packing principles due to the extra space and weight taken up, I've found a way of carrying a system consisting of four methods of making potable water, and make the entire kit including the water bottles and cases weigh just 324 grams.

Clockwise: Vargo titanium water bottle, Katadyn Micropur Forte tablets, Platypus Plus 1L bottle, and Sea to Summit padded pouch (M)

Inside the pouch, left to right: filter cleaning syringe, Sawyer Mini, and Steripen Freedom

If you want to go even lighter, you can. It's possible to keep most of the functionality of this kit while reducing it to around 200 grams, which I will tell you how to do at the end of the article. Below are the steps I use to get really clean and safe drinking water.

Water Filtration

Any good system should start with a water filter, which mechanically removes sediment, parasites, protozoa, and bacteria. For this task, I've chosen the Sawyer Mini. It uses the same technology as kidney dialysis machines, is good for 100,000 gallons, and has an absolute pore size of just 0.1 microns (small enough to filter out bacteria and bigger). This filter, which I would consider the best and lightest on the market, costs less than $30. If you don't drop or freeze it, it will last you a lifetime.

To support the filter, I also have a small syringe for back-flushing the filter when flow rates slow down every few dozen gallons (no cartridge needs to be replaced), and a 1L Platypus Plus Bottle from which to filter the water. This collapsible bottle is designated as my "dirty" water bottle.

The Sawyer Mini screws onto the Platypus Plus water bottle, as well as most generic, store-bought plastic water bottles, and then filters directly into my Vargo titanium bottle.

Water Purification

Different from filtration, purification involves chemically or otherwise killing or disabling everything in the water. Viruses will pass through the Sawyer Mini's membrane, so that's where the Steripen Freedom comes in. It uses UltraViolet light to deactivate the DNA of viruses, bacteria, and other nasties in the water.

The mouth on the Vargo Titanium bottle is wide enough to accommodate the Steripen Freedom.

It also works as an excellent backup in case your filter is damaged and you're unaware of it. I wouldn't use just the filter on its own – I treat it as the first step. So to recap: first you filter the water from the dirty plastic bottle by squeezing it through the Sawyer, then you purify it with Steripen's UV light. Assuming everything works as planned, that's where it stops and you have clean water.

Backups in case of technological failure

But sometimes things don't go as planned, and these are some pretty high tech gadgets. Both the Sawyer Mini and Steripen Freedom can break if dropped, and the Steripen can also run out of battery, so what then?

Because the Vargo Titanium water bottle I use is metallic, it can be used to boil water on a fire. Whether that's a campfire or a gas stove, bringing water to a rolling boil for at least 1 minute is a sure way of destroying anything in it.

You'll also notice that I have 50 water purification tablets. I use Katadyn's Micropur Forte, and the whole set weighs just 4 grams. They're very easy to use – just drop one tablet into a liter of water and wait for half an hour before drinking. Their expiry date is usually a few years down the line and the ability to purify 50 liters for just 4 grams is a great backup – and no fire needed. I usually keep this in my first aid kit, as that ensures I always bring them with me.

How much time does this take?

If you've never used such a system before, you might think this is a whole lot of hassle. Trust me, compared to having parasites or hepatitis, it really isn't. But the best thing is that this system is *fast*. The sawyer will easily filter the 650ml of water that my bottle can take in less than a minute, and the Steripen treats 1L in about 1.6 minutes. Add a couple of minutes for taking this system out of your backpack, filling the dirty water bottle up, and putting everything back, and you're talking about having really clean water anywhere you go for about 5 minutes.

Recharging on the go

I normally use an Android phone and so I already have the same micro USB charging cable that the Steripen Freedom uses. I just carry one for both devices.

If however I'm expecting to be away from a mains power supply for some time, I also bring my charging kit (not counted in the weight above). It charges both my phone, flashlight, and Steripen. The total weight of the charger, cable, and two 18650 batteries with 3400 mAh each is just 135g. Plus, I can always use the third 18650 battery I already have in my flashlight (a NiteCore P12).

Left to right: ML-102 18650 charger can charge any USB device, two 18650 batteries, my Micro USB cable, and a Mini USB cable for charging the batteries

The ML-102 is fantastic. It has LEDs that tell you when you're charging or discharging a battery and when a battery is charged, and it can charge any USB device. It has two ports: a USB port for charging other devices from the 18650 batteries, and a Mini USB port for re-charging the batteries from any USB device or mains adapter.

Nitecore's 18650's hold a charge for years, have about 500 charging cycles, and each battery holds 1.5 times as much power as my smartphone's internal battery. With a couple, I can fully charge my smartphone three times. This has been a lifesaver when traveling.

Going even lighter

The titanium water bottle weighs 106g, and really could be replaced with any container (such as a cup) wide enough to stick a Steripen into. Additionally, you could put the rest of the kit into a spare pare of socks or wrap it in other clothing, and save over 40g off of the padded pouch I use for protection. Personally, I don't want wet items mixed in with my clothing, but it's workable.

You could also preserve boiling capability by bringing a titanium cup with you instead of the bottle.

Additional notes and tips

• To recharge the Steripen or the batteries from the mains, you'll need a mains USB adapter. Since like most people I already have this for my smartphone charger, I've not listed it above, but if for some reason you're traveling without a smartphone, keep this in mind.

• Another point is that the filter cannot be frozen with water inside, as the water will expand and damage the membrane. After you use it once, assume that it will never be completely dried out and that there's always some water inside. This means two things:

1. Never check your filter – always have it in your carry on bag. Luggage in an aircraft's hold may go below freezing. I've never been hassled over it in my carry on in over a dozen flights.

2. When outside in sub-zero temperatures, keep it in a shirt pocket close to your torso, rather than in your backpack. If sleeping in a sleeping bag, bring it in with you there, too.

• After prolonged use, the inside of the Vargo Titanium water bottle can easily be cleaned by filling the bottle with water, adding some salt, and then shaking it vigorously.

• Finally, I should note that the above system does not remove chemicals in the water. If you suspect that factories or farms have been dumping chemicals into the water, the equipment I'm suggesting won't deal with that. If such an eventuality is a serious possibility, consider bringing an activated charcoal filter extension. Katadyn make a lightweight plastic version that can probably be tubed onto the setup above.

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(Although the links above are Amazon affiliate links, none of the aforementioned companies are sponsoring me to advertise their products, they have all been purchased with my own money, and I rely on them myself.)