Water Purification

Although the water may look pristine and clear, looks can be deceiving. There may be a dead animal carcass 100 yards upstream, pollution runoff from a nearby abandoned mine, or more commonly, harmful microbes in the water. The most common microbe is Giardia (here), which is a protozoan parasite that, when consumed from infected water sources, can result in intestinal illness.

Identifying Water Sources
Identifying pure water sources is an important skill to learn. Whenever possible, ensure your water source is clear and moving. In general, avoid the following:
  • Stagnation- these pools may have been stagnate for years, become more concentrated with animal feces and whatever microbes are growing within. Other times, a seasonally stagnate lake may develop when the incoming/outgoing stream ceases during the summer. At times, this may be the only source for many miles and can be a necessary risk.
  • Color- water doesn't have to be clear blue to be safe to drink, but without having considerable experience, try to avoid water that is off in color. Sometimes water may be brown due to mud, which can be safe to drink, but it might also include animal waste or runoffs. In general, the color of the water doesn't tell if it's safe to drink.
  • Foam- when there is foam on the surface, that generally indicates some form of pollution.
  • Algae- this can be from either good or bad sources. Algae in stagnate water is a bad sign, while algae in moving water can be normal and healthy, so it's important to understand where the water is coming from. Spring water almost always has algae growing at the source, which is a good sign.
  • Off Taste- especially in areas with current or former mining activities, there can be runoff in the water that might even be poisonous. Be very cautious of any long-lasting bitter taste, which may be alkali water. Usually, this water is accompanied by brown or dark orange algae (often only visible by examining the bottom of the water source).
  • Plant & Animal Life- even if water is crystal-clear, be extremely cautious when there is no plant or animal life nearby. The animals are smart enough to avoid water tainted with arsenic, for example, and plants can't grow around it, so understand these signs.
Purification Options
Here's an overview of the various options for purifying water:

MethodPros Cons 

No Treatment
- some experienced hikers rely on their knowledge of identifying pure sources. They may also spend years drinking from certain "bad" sources, in small doses, to develop a tolerance.
  • Lightweight- no weight!
  • Inexpensive- free!
  • Risky- inexperienced hikers will not understand safe sources. Even experienced hikers may have immune system differences that do not allow for building immunity against protozoans.

Chemical Treatment
- there are various options for treating water with chemicals, either in commercially tablet form, or by using bleach or iodine.
  • Lightweight- a small bottle of tablets or bleach/iodine can last a weekend or longer
  • Safety- these treatment, when applied as directed, can safely kill most microbes.
  • Taste- the most noticeable con is the off-taste of these treatments
  • Expensive- many of the commercially-available tablets are expensive, especially when considering longer trip.
  • Disposal- empty glass tablet/liquid containers need to be carried before disposed, adding a little bulk and weight.

Boiling Treatment
- it's possible to kill microbes by boiling water, usually for 20-30 minutes (after the water has reached a boil.
  • No Extra Equipment- provided you already have a cooking source and water pot, you don't need to have any additional equipment.
  • Little Effort- one you've got your boil going, you can sit back and relax. 
  • Heavy- boiling water requires the use of fuel, which is heavy and bulky, and a heavier stove which supports the long boil time.
  • Expensive- fuel adds up
  • Time-Consuming- it takes a long time to boil water, and then wait for the stove to cool.

UV Treatment
- there are commercially-available battery-operated devices that are put into water to be treated.
  • Effective- the manufacturers claim that the devices kill most protozoa, bacteria, and viruses
  • Little Time/Effort- the manufacturers claim that the devices can treat 1 liter of water in around 90 seconds
  • No Filtration- if you treat dirty water, the water will still be dirty
  • Expensive- these devices tend to be more expensive
  • Requires batteries- once the batteries run out, you have no way to treat water
  • Requires bottles- these devices aren't useful if using a bladder-type water container. Bottles are heavier than bladders.
Pump Filtration
- the most common purification method used by hikers involves filtering water with a pump device.
  • Effective- most 0.22 micron filters will filter out all microbes (but not viruses, which are smaller)
  • Resourceful- you may be forced to drink from muddy water, which can actually turn clear once it's filtered.
  • Inexpensive- pumps can be purchased for a reasonable price and the replaceable filters can last for years.
  • Effort/Time- taking a 20-minute "break" to pump water is not really much of a break at all. It requires pulling out the pump, assembling it, then (often with 2 people) holding the source line steady and pumping into the container.
  • Weight/Bulk- even lightweight pumps get heavier after use, since the filter is saturated, and all pumps take up pack space.
  • Bugs- many water sources are plagued with mosquitos and other annoying bugs. Pumping forces you to spend time next to water, often with hands full and unable to swat at the bugs.

Gravity Filtration
- some hikers advocate for a gravity based system that filters the water with little effort. The concept is that you use a bucket-like device to scoop water from the source, then hang that bucket-device from a tree. Then, a hose comes down from the bucket, through a filter, and into your drinking container.
  • Effective- most 0.22 micron filters will filter out all microbes (but not viruses, which are smaller)
  • Resourceful- you may be forced to drink from muddy water, which can actually turn clear once it's filtered.
  • Little Effort- after scooping water from the source and lifting it into place, gravity does all of the work.
  • Weight/Bulk- in addition to having the weight of the filter, this method requires an additional bucket-like device. Even though these are usually lightweight, collapsible buckets, they add to the pack.
  • Time- this method works well at the end of the day (presuming you ignore the advice to avoid camping at a water source), but otherwise requires taking a break to filter. Gravity filtration can take longer than pump filtration.
Straw Filtration- this method allows you to fill your water bottles directly. The top of the water bottle has a "straw"-like device with a built-in filter. As you drink, the water is filtered.
  • Effective- most 0.22 micron filters will filter out all microbes (but not viruses, which are smaller)
  • Resourceful- you may be forced to drink from muddy water, which can actually turn clear once it's filtered.
  • Little Effort- after filing your water bottle, you can drink purified water right away.
  • Requires bottles- most of these devices require the use of a bulkier bottle, usually about 1-liter in volume. This can be great for short hikes, but less useful for long hikes that requires more than a liter of water.
  • Weight- these built-in filters, along with their associated bottles, are heavier. If you want to have more than one, you're carrying additional filters for each of these containers.
In-Line Filtration- this method allows you to fill your drinking containers directly from water sources. Then, a smaller filter is contained within an in-line hydration system.
  • Effective- most 0.22 micron filters will filter out all microbes (but not viruses, which are smaller). Many commercially-available filters are said to last for many years.
  • Resourceful- you may be forced to drink from muddy water, which can actually turn clear once it's filtered.
  • Almost No Time/Effort- after filing your containers directly from the sources water, you can put your pack back on and keep hiking (see increasing mileage).
  • Easy Decisions- instead of having to decide whether to stop at the current water source or hope the next one exists, when filing a container requires almost no effort, you can always top off your water without having to consider the time/effort involved in pumping.
  • Restriction- drinking from a tube with an in-line filter requires slightly more suction than when drinking from a line without a filter.
  • Water Weight- you may find that you're able to fill-up more often and, therefore, carry unnecessary water between water sources. Depending on your hiking location and the availability of water, you may need to decide the ideal amount of liters to carry.

Our Recommendation
For general hydration strategy and our recommendation for gear, see trail hydration.

Lightweight Hiking Concepts