ArticlesHow to Choose

Avoid the Beaver and Save the Weight: How to Choose a Water Filter

It hit me about halfway up the mountain. It hit with that instant urge. It was coming and now, so I ran into the woods, didn’t have time to dig a hole, dropped my pants around my ankles, and that was the start of a six month bout of beaver fever.

About halfway up the mountain, she started to have the runs. It just so happened that there was a road and visitor center at the top of the mountain, so she kept on walking. About every ten minutes, she had to go. We feed her all our water, but by the top of the mountain, she was completely dehydrated.

These are two examples of situations that occurred on the Appalachian Trail because of foul water. The first happened after drinking from a spring that was reputed to be pure, and the second occurred probably because of cross contamination of a water filter. Both show the importance of having a good way to treat water and the second shows that even when doing everything right, a good system may have a serious weakness that should taken into account.

When traveling light and fast, a third factor that must be considered is the weight of the system. Ideally, a water purification system will create potable water, have few weaknesses, add little chemical taste and weigh very little.

Water Purification Systems

There are several types of water treatment systems for backcountry travelers. Those that are the most popular are simple pump filters and chemicals like iodine. Variants of pump filters include water bottles with built in filters, inline filters for hydration systems, and gravity feed filters. A relatively new category is an electronic system. Each has advantages and disadvantages.

Pump Filters

Pump filters are perhaps the most popular backcountry gadgets right after stoves with many different models on the market. But three models are by far the best sellers on the market: Katadyn Hiker, MSR MiniWorks EX, and the MSR SweetWater. Each of these filters provides approximately the same advantages. They make potable water very quickly, for small groups not a lot of work is involved, the taste of the water is either the same as the source or slightly better, or they filter out muck in the water. They also share the same disadvantages. You have to pump them to make water, so it’s one more thing you have to do in the morning, at lunch, or before dinner. They’re heavy. You have to watch for cross contamination, which is what happens when you contaminate the clean hose with the dirty one through contact when filtering or during storage.

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Among these three filters, there are some variances that merit discussion. The Hiker and SweetWater each use a paper type filter and the MiniWorks uses a ceramic filter. The ceramic filter and the filter in the SweetWater can be cleaned when clogged, but the filter in the Hiker must be replaced when it clogs. All three will clog. The SweetWater tends to clog more often and quicker than the MiniWorks. And the Hiker seems to avoid clogging for a good amount of time, but when it does, that’s it.

Also, the MiniWorks is 4 ounces heavier, but it does include a nice system to screw a Nalgene bottle onto it. This will help avoid cross contamination, but to take advantage of this, you have to carry a heavy bottle or a bladder with an awkwardly large opening. The Hiker has two long tubes that can quickly become cross-contaminated, and require careful management when filtering and storing the filter.

All three filters also vary in speed of output. The Hiker is by far the fastest filter, and if you count the amount of cleaning, the SweetWater is the slowest. The MiniWorks is faster than the SweetWater, but still agonizingly slow compared to the Hiker.

Having used all three of these filters extensively, when I use a pump filter, I’ve settled into using a MiniWork EX. I like the ability to quickly clean the filter and the long life of the ceramic filter. I also like the less hassle with managing the filter hoses against cross contamination. I deal with its slow speed.

Filter Variants

A couple of filter systems don’t use a pump to force the water through the filter. The first and popular choice is a water bottle, like the Katadyn Exstream, that contains a filter. When the bottle is squeezed, the water is forced through the filter and down a straw to the awaiting mouth. These water bottles tend to be very light, but sometimes the water doesn’t flow fast enough. I know one sponsored hiker who removed the filter from the bottle and just used AquaMira to treat his water. Another option is the Katadyn Base Camp. With the Base Camp, you fill a bag and let gravity force the water through a filter. This is a great system for large groups if you have the time to let the filter run, usually overnight. Both of these systems can suffer from cross-contamination. And unless the tube is run correctly or run directly into a threaded bottle like a Platy, the Base Camp is very prone to cross-contamination. Another variation of this is filters that are spliced into the hose of a hydration system. Hydration system filters seldom have cross problems, and typically weigh much less than pumps or the Base Camp. If you use a hydration system, a spliced filter can be an outstanding filtering system choice, because it’s fast and light. A main disadvantage is that none of them are field maintainable. When they clog, you either change the filter or figure out some other way to make potable water.

Electronic Purifiers

A new category of water treatment systems is electronic. Two main devices dominate this category: SteriPen’s SteriPen and MSR’s Miox. Both of these require batteries, but they function differently. The SteriPen uses UV light to kill the bugs in the water. It’s main problem is in dirty water where it has a problem with getting everything. It’s second main problem is that it’s not hard to imagine that the bulb would be easy to break, so a solid storage container is a must, and with the container and unit, it’s heavy. It’s also expensive. The MSR Miox treats water by creating a chemical from sea salt, water, and electricity. The dosage is adjusted for the amount of water that is being treated. After the device does its thing, the chemical is dumped directly into a bottle. It’s allowed to mix, then the threads are treated and then the waiting starts. I’ve found that I’ve had to double to triple the dosages in the BWCA to make the testing strips that come with the unit turn the proper color. The Miox is lightweight, but uses CR123 batteries camera batteries, which are becoming increasingly harder to find as digital cameras are using their own proprietary batteries. Because both of these systems use batteries, there is a risk of failure when the batteries run out, so it’s a good idea to bring extra. The Miox does have an advantage that it can treat large amounts of water quickly, but if you’re worried about crypto, you have to wait six hours. This is good for large groups. Plus both of these systems don’t require any manual labor of pumping.

Chemical Water Treatment

The last category of water treatment systems is chemical water treatment. The main products that stand out are Mcnett’s Aquamira (same as Pristine), Katadyn’s Micropur Tablets, and various Iodine systems. First, Iodine. Some people have health problems with Iodine and particularly with using Iodine for extended periods of time, and Iodine tastes bad, and Iodine doesn’t kill everything. It really has been surplanted by these other chemicals. Micropur Tablets take awhile to dissolve, but weigh very little and work well. They are very expensive per quart, which is the main downfall. These make a great backup plan to pumps and filter or work well as something to throw into your ditch kit just in case something bad happens.

Aquamira and Pristine are two-part treatment systems. You mix a certain number of drops of chemical A with the same of chemical B. Wait for the reaction to occur and then dump it into your water and wait 30 minutes. Then you have drinking water. The big question that everyone has is why do the Pristine time frames differ from the Aquamira time frames. To find out I called both companies. Lindsey the customer service representative from Aquamira said that even in cold water down to 33 F, you only have to wait 30 minutes. She recommended doubling the dosage in low temperature conditions. She also said Aquamira works against crypto in the same time frame, which the MSR Miox does not do. One thing that she added was that the water should be clear backcountry water, not murky sludge like water which the EPA tests on. Aquamira is not EPA approved yet, but is currently going through the process.

Pristine’s customer service person told me was that the two brands are manufactured by two different companies, but that they could be considered sister products. They are pretty much the same thing. So, I asked her about the time frame difference between what I heard from AquaMira and what is listed on the Pristine website. I was concerned that the AquaMira is a stronger version of the chemical… For cold water, she said that it would work in the 30 min. and kill crypto, but they choose to be more conservative, because the lower temps slow down the molecules of the chemical. She also recommended a double dose in cold water.

The key when using AquaMira or Pristine is to treat clear water, so you should try to filter out as many particles as possible when filling up your water bottle. A good way to do this is with either a coffee filter (slow) over the opening or an old nylon pantyhose (faster). If you do this, not only do you remove floaters, but help the chemical along. In questionable water, you may want to increase dosages and wait time to give the chemical time to penetrate the floaters and get the bugs.

Both of these chemicals have the advantage of taking little work to treat water, they don’t change the taste of the water, they work quickly, and they weigh very little. Each weigh about one ounce for 200 gallons and less if you repackage them into smaller dropper bottles, which are sold in kits at some websites. The only disadvantage is if the water is sort of cloudy, you’ll be drinking cloudy water, and that you have to mix the chemicals.

Which to Choose

As a lightweight canoeist or kayaker, the choice seems clear (bad pun). AquaMira and Pristine are the lightest system on the market. It requires very little work. The water tastes good and not chemically. And it creates potable water in 30 minutes. In cloudy water, bring a pantyhose filter or fill a container and let the cloudiness settle out overnight.

If you’re going into an area with cloudy water, a pump filter should be considered to remove the cloudiness from the water. In this case, the choice isn’t so clear. The Hiker filter is the lightest, least hassle to use but has real cross-contamination possibilities. The MiniWorks is heavier, requires a heavier bottle, but is more reliable in the field. An ideal system would be the lighter inline filter for a hydration system.

If you want very little work in a cloudy water area and don’t want to mess with chemicals or pumps, then a gravity feed system is the way to go. These are lightweight, easy to use, work while you sleep, and make good tasting water. You do have to carry extra water at the start of the day, which is a big disadvantage though.

What Do I Use

On some trips, I bring a MSR MiniWork EX. These are usually shorter trips with other people. We generally share a filter and fill our own bottles. On longer trips or solo trips, I use AquaMira. It’s light, and the places I paddle have clear water.