Next to staying warm, the most important survive and comfort factor is to make sure you drink an adequate amount of safe water. This often means you need to carry water and be prepared to treat water. Not all locations have a continuous supply of safe water. Failure to treat the water can result in severe illnesses which would minimally make your trip less enjoyable, and in the worse case be life threatening.
Knowing how much water you need is important so you have enough but don’t carry several extra pounds of unneeded water. I determined my water needs but weighting myself, engaged in activities, and then weighted myself at the end. My typical water consumption when moderately active is 1L for every three hours when it’s 30-60F, around 1L for every 1.5-2 hours 60-80F, and 1L every hour when it’s more than 80F. When engaging in vigorous activities such as running I use around 3x the water. Cool weather 1L/hour, extremely hot weather 3L/hour.
When in the back country I use a Geigerrig hydration system. Geigerrig has two bladders, one which holds water, and the other can be pumped up with air which enabling good water flow, even when the optional in-line filter is installed which is how I treat suspect water. On group trips I use the Geigerrig in-line filter between a 3L Big Zipper SL and a Platypus Water Tank as a gravity filter. In the winter I often bring extra fuel and boil the water a few minutes and carry wide mouth Gatorade bottles because it’s one of the few light weight drink containers which can handle boiling water poured into them without melting. In urban areas I carry a Zojirushi Double Walled Mug because it can easily be used one handed, locks so it doesn’t open accidentally, pours at the perfect speed, the mouth is wide enough for ice cubes, and liquids stay fairly warm or cold for 24 hours.
In the US, tap water is safe to drink almost everywhere and not treatment is required. This varies in other countries. In the back country of the US (streams, lakes, rivers) the the most common issues are typically larger organisms: bacteria, cysts, etc. If the water is particularly cloudy, chemical and UV treatments are are less effective with these, especially cysts and bio-films. Outside the US, you might also need to deal with even smaller organisms like viruses. A basic filter is not effective, you need a “purifier” filter. The good news is that chemical and UV are highly effective against these smaller organisms, so often people will filter and then use chemical or UV to be completely sure the water is safe.The best place to take water is from the top 1/2 inch of a lake. Constant exposure to UV light from the sun tends to purify the top layer of a fixed body of water.
Chemical treatments are small, light weight, and don’t clog. First, let me suggest that you should skip to common chemical treatments of iodine and bleach. Both chemical are more effective than nothing… but both chemicals are less effective than Chlorine Dioxide water purification. I like Chlorine Dioxide because it is effective and has less of a “taste” than most other chemical water treatment. Just after treatment, the water can taste a bit like pool water just after treatment and becomes less pronounced if given a bit of time to “breath”. In clear water it’s fully effective in 30 minutes, in cloudy water everything but cysts are killed in 15 minutes, with the cysts taking up to 4 hours to neutralize. I often used Kaytadyn Micropur tablets because they are so simple. I have also used Aqua Mira treatment drops. There are a few other chlorine dioxide based treatments tablets made by Aqua Mira, and the MSR MIOX system. The tablets from Aqua Mira and Kaytadyn have three times the chemical load of the suggested dose using Aqua Mira drops making them more effective but also having a stronger taste.
Gravity and “Squirt” filters
Gravity have become quite popular since they filter almost as fast and pumps with little work required. The downside is that you need a large contain to hold “dirty” water. Originally gravity filters were mostly home-make or very heavy systems designed for base camps. A number of companies sell purpose designed gravity filters that are appropriate for backpacking including the Platypus Gravity Works, MSR Autoflow and Katadyn Basecamp. I like the feeder for the Platypus, but I think the clean reserve is less than ideal. The Platypus Water Tank is much better because it can sit on the ground with the opening toward the top.
There are a number of filters which are designed to go inside sports bottles, attached to a hydration system tubing, or are thick straws like LifeStraw, that you suck the water through. Historically I didn’t like any of these systems because you had to create suction with your mouth to pull the water through. This is fine around town at lower elevations. If you are slightly out of breath after a long climb, and you are at 14k ft, having to apply sufficient suction can be very difficult. These days a number of companies are putting the filters in soft bladders that you squeeze to push the water through the filter which works pretty well. Katadyn BeFree and Sawyers Squeeze.
Pump based water filters used to be the go-to water systems. They are very well suited to situations when water hard to access, like in very shallow pools. They are effective, long lasting, and some have charcoal elements which will remove some chemicals and improve water taste. Filters tend not to catastrophically fail, but as the age they can filter 4x slower than a new filter. If you use a filter when the nights get below freezing, make sure to either fully drain your water filter, or keep it warm so it doesn’t freeze. Filters are particularly useful if you are in locations which are hot and have few sources of water. You can “camel up”, drink as much water as you can at the source so you don’t have to carry it. There are lots of filter options.
UV / Solar
Recently, a number of products have come to market that use UV light to purify water. The most popular are the Aqua Star and the SteriPEN which is now owned by Katadyn. The nice thing about the using UV light is it will purify reasonable clear water in something like 60 seconds. Just scoop up the water and turn on the UV source. When the water is cool and good tasting, this can be quite the treat. The downside of the UV systems are that they don’t work well with cloudy water, and the systems is prone to fail, particularly in colder conditions. It you decide to use a UV system, bring a a backup system. Most UV systems needs a wide mouth container so the typical Playtpus bladders don’t work with it.
Solar water disinfection (SoDis) is a highly effective way to treat water in sunny locations if you aren’t on the go. Simply fill up a plastic 2 litter or smaller bottle with water, and put it in the sun. In full sunlight it will be safe to drink in 6 hours.
Three minutes of boiling water is also highly effective went dealing with biological containments. The downside is that you might need to carry extra fuel, and in hot weather, you don’t get safe, cold water to drink.
There is significant evidence that poor personal hygiene (e.g. not washing hands during food prep) is the most significant source of contamination in the back country, so some people don’t purify their water sources. I think this is an unnecessary risk and don’t recommend this approach. One of the early scholarly look at this was performed in 1984 about Giardia Lamblia and Giardiasis in Sierra Nevada and a more recent study from UC Davis from 2003 seems to indicate that the water in most of the high sierras is still pretty clean. You can read their technical article An Analysis of Wilderness Water in Kings Canyon, Sequoia, and Yosemite National Parks for Coliform and Pathologic Bacteria. Related articles include Cyst acquisition rate for Giardia lamblia in backcountry travelers to Desolation Wildereness and Evidence based Medicine in the Wilderness: The Safety of backcountry Water.
When engaged in activities away from home or the office it is good to have water readily available.
Nalgene & Plastic Water Bottles
Nalgene water bottles have been one of the most iconic and commonly used water bottles. This is understandable because they are nearly indestructible, don’t give beverages a “taste” like aluminum can, and have a wide mouth which makes them easy to fill. Boiling water doesn’t melt them which make them particularly useful in the winter as hot water bottles.
Also popular are sports bottles that are flexible enough to squeeze with sealing squirt tops which was originally popularized by cyclists. There are several companies which make insulated bottles, but I haven’t found any which can keep my drink cold or hot for more than an hour.
Empty bottled-water containers are a cheap and lighter alternative to the classic Nalgene water bottle and are surprisingly durable. They are also a good size to hang on your shoulder strap (adventurer racer style) which gives easily access and can provide a bit of weight to counter balance your pack
In recent years people have become concerned about polycarbonate based plastic which might pose a threat to pregnant women and young children. Nalgene now makes a number of bottles which don’t leach chemicals into water.
Metal canteens were a commonly used water container for outdoor pursuits before plastic water bottle became available. In recent years they have been making a come-back as people are concerned about plastic leaching harmful chemicals into their drinks, a desire for containers which are ultra durable, and with the advent of the double walled vacuum container the ability to insulate.
For modest amounts of water I think metal containers can work well, but when the amount of water exceeds 1L I believe it’s best to use lighter weight water containers.
Some of the more popular metal water bottles include those made by Hydro Flask, Klean Kanteen, Yeti. I am very fond of the double walled insulated water bottles made by Zojirushi. Snowpeak makes some beautiful titanium water bottles.
Platypus was one of the first companies to make flexible bladders designed to carry water and other beverages. The original models could be folded up into a small space when empty and were hand held with a small opening for filling and drinking. The narrow mouth could be a problem since it was challenging to clean, dry, and in some situations fill. Since those early days a number of other companies now make flexible water containers including Vapur, Hydrapak, and MSR.
There have been a number of innovations, largely related to the openings. Several companies have paired the soft side bladders with larger opening to make then easier to fill and clean. There is also significant cross over between water bladders and hydration systems discussed below.
Camlbak might have been the first company to make a hydration system. They combined a flexible water bladder which could be kept inside a backpack with a plastic tube and “bite” valve that allows the user to drink without using their hands.
Several other companies including Platypus now make hydration systems. For several years I used the Platypus 3L Big Zip SL. It is light, durable, and collapsible, and competively priced. Today, I use a pressurized system made by Geigerrig.
BPL’s Water Quality Technologies and Trends. The most complete review I have seen, but now out of date was the US Army’s Commercially Available Water Treatment. That site does have a number of resources about safe water.
If you aren’t moving much and it’s sunny, you can put the pop bottle filled with water in the sun. The sun’s UV will kill off biological threats within 6 hours. Otherwise, Aqua Mira or boiling will be the cheapest in the short term.