Water Treatment: Filter vs Purify-Appalachian Outfitters

Water Treatment: Filter vs Purify

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One thing that every backpacker shares, no matter where they are hiking, is their need for water. Most backpackers will need to drink at least one liter of water per two hours of hiking. Water is heavy, and between a water bladder and a couple of bottles, the most you can carry in a backpack is about 5 liters, meaning that you will need to find water during your trip. You never want to drink water straight from a stream, river, or lake that is not treated for waterborne pathogens first. Besides being full of dirt and other debris, any outdoor water source can contain a variety of protozoa, bacteria, and viruses that could make you sick, so the solution is to always treat your water before use. With so many different products claiming to clean water, how do you choose which one to buy?

Filtration Vs Purification

First, what is the difference between water filtration and a water purifier system? You often hear filtration and purification used interchangeably, but they do not mean the same thing. Filtering water means running the water through a material that will remove something from the water, and there is no defined standard for a water filter to meet.  That means a water filter could be a microfilter used to remove bacteria and protozoa, or a water filter could be running water through your sock to remove sticks and leaves.

Most outdoor brands will sell water filters that fall into the category of microfilters.  Microfilters can remove debris, bacteria, and protozoa, but do not remove viruses, which may be adequate depending on where you will be traveling.

Alternatively, water purifiers have strict standards they are supposed to adhere to for dealing with protozoa, bacteria, and most importantly viruses.  Water purifiers can fall into a few types, including chemical water treatment, UV water treatment, and exclusion purifiers, which look and operate similarly to some of their microfilter counterparts.  While a water purifier might function by filtering out all these microorganisms, it is important to remember if it deals with viruses, it should be classified as a water purifier, not water filter. 

While virus can be found anywhere, if you are traveling to remote locations around the US or Canada many people are fine with only a water filter.  As a general rule, the more human traffic an area sees, the higher the chances of waterborne viruses being a problem.  So, in areas that see a lot of foot traffic, like some of our more popular national parks, a purifier is preferred.  Additionally, if you are traveling to a less-developed country, viruses can be more prevalent, and a water purifier should be considered over a water filter.

Types of Water Treatment Products


By far, the most well-known way to treat water is by boiling. Water needs to come to a rolling boil to kill most bacteria and viruses, and it is recommended to let it boil. According to data from the World Health Organization, most waterborne pathogens are killed in water at 160 degrees, so bringing it to a rolling boil, will have surpassed that temperature and will be safe to drink once cooled.  Although boiling is effective in removing microorganisms, it will not remove any debris from the water and is a time-consuming process. Plus, who wants to sit on the side of the trail during their hike to boil water and then wait for it to cool?

Boiling water over campfire


Tablets are great to keep in your backpack as a backup if your filter fails or to have in an emergency. There are two main types of tablets: chlorine dioxide and iodine. Iodine based tablets are effective against viruses and bacteria, but have been known to not kill the protozoa Cryptosporidium.  Clorine dioxide tablets will kill viruses, bacteria, and protozoa, including Cryptosporidium, the time required varies from about 30 minutes to 4 hours based on water temperature and clarity, so be sure to follow the manufactures instructions.  The tablets do not filter any debris out, so you could either pair them with a filtering system or collect the water from a moving body of water to try and avoid dirt, rocks, and other debris.

Katadyn Micropur Purification Tablets

Micropur Purification Tablets

Type: chlorine dioxide

Effective Against: bacteria, viruses, and cysts

Amount: approx. 1 liter per 4 hours


Pros: inexpensive and good backup method

Cons: does not clear water of debris, takes a long time to work

Ultraviolet (UV) Light Purifier

Treating water using UV light is another way to purify your water. UV light pens do not kill bacteria and viruses, instead, it makes them unable to reproduce, making the water safe to drink. UV treatment is less effective in dirty water because any debris floating in it can obstruct the UV light rays from reaching the bacteria and viruses. Collecting water from a moving body of water can typically give you more clear water. These are also great to have for an emergency at home or traveling where you need to sterilize tap water.

Steripen Ultralight UV Purifier

Steripen Ultralight UV Purifier

Effective Against: bacteria, protozoa, and viruses

Amount: 1 L per 90 seconds

Weight: 3 oz

Pros: small size

Cons: does not work in debris-filled water

Gravity Filters and Purifiers

Gravity systems are a great option for backpackers. Once it’s set up at basecamp and running you can basically forget about it until it’s done filtering your water. The big advantage of using a gravity system is that you can purify a lot of water with little effort. Most can only remove bacteria and protozoa, but some are also effective against viruses. You can connect the gravity bags to your water bottle or bladder to easily refill them.

Katadyn Gravity BeFree Microfilter 3.0L

Katadyn Gravity BeFree Microfilter 3.0L

Effective Against: protozoa and bacteria

Amount: 2 liters per minute

Weight: 7 oz.

Pros: easy fill, hang, and clean

Cons: does not remove viruses


MSR Guardian Guardian-Gravity-Purifier

MSR Guardian Gravity Purifier

Effective Against: viruses, bacteria, protozoa, sediment, and microplastics

Amount: 1 liter per 2 minutes

Weight: 1 lb. 3 oz. 

Pros: filters up to 10L, two-stage purifier, easy clean system

Cons: cost


Bottle Filters

Bottle filters are light-weight, low-hassle options for filtering water on the go. The bottles have a filter attached to the lid. Simply fill the bottle, preferably with moving water, and squeeze and hydrate. A big downside to bottle filters is that they don't hold a lot of water, so you might need a water bag if your water source is far from camp. 

Katadyn BeFree Microfilter 1.0L

Katadyn BeFree Microfilter 1.0L

Effective Against: bacteria, cysts, and sediment

Amount: 2 liters per min

Weight: 2 oz

Pros: easy to use on the go

Cons: only holds 1 liter


Pump Filters and Purifiers

Pump filters are a lightweight option to filter and purify on the go. The biggest advantage to pump filters is the variety of options out there and the things that can be removed from the water.  All of them will work on bacteria and protozoa, but some models with remove chemicals and toxins and some will even remove viruses. Most are easy to clean, although some can't be cleaned at all.  Depending on the clarity of the water you are filtering, their filter elements can have long lives, making these pump filters perfect for the avid backpacker that needs to make sure that the water they are drinking is clean and free from all contaminants. 

MSR MiniWorks EX

MSR MiniWorks EX

Effective Against: bacteria, chemicals, toxins, particulates, protozoa, viruses

Amount: 1 liter per minute

Weight: 1 Ibs

Pros: filters/purifies everything, easy clean, lightweight

Cons: fragile ceramic filter


MSR Guardian Purifier Pump

MSR Guardian Purifier Pump

Effective Against: bacteria, chemicals, toxins, particulates, protozoa, viruses

Amount: 2.5 liters per minute

Weight: 1 Ibs 1 oz

Pros: filters/purifies everything, self-cleaning, long cartridge life

Cons: Cost


If you have any questions or would like to discuss more product options, feel free to come to our store and ask our staff or email us using the "Contact Us" button at the bottom of our page

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