How to Choose A Water Filter/Purifier

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There are so many different types of water filters and purifiers, and deciding which to bring on your trip can be overwhelming. I’d like to help make it easier to understand the differences so that you can make the best choice.

There is no ‘perfect’ choice here. Each type has different benefits and disadvantages. All you can do is choose the one that best fits your needs.

As an example, if you’re going on a solo hike you want something small, quick, and lightweight. Whereas when going on a group camping trip you need something that can treat a large amount of water.

Whether you need just a filter, or a purifier – or both, depends on a number of factors.

Filter or purifier? What’s the difference?

These are the two main categories to treat water: filters and purifiers. The difference between the two is the size of the microorganism each one combats.


Filters use a physical element to remove bacteria (for example Salmonella) and protozoan cysts (like Cryptosporidium and Giardia) from the water. Those biological pathogens are the main concerns when traveling in the U.S. and Canada.

Most filters won’t filter out viruses, because they are small enough to pass through the filter’s pores.


Purifiers neutralize bacteria, protozoa, and viruses. Viruses are too small for filters to catch, and if you’re traveling outside of the U.S., in an area where you’re concerned about viruses or there’s a lot of human/animal activity, then you need a purifier for sure.

Although there are some filters that have pores small enough to capture viruses, any purifier can definitely provide protection from viruses like hepatitis A, norovirus, and rotavirus.

There are many different forms of purifiers, such as a chemical purifier and UV purifiers, just to name a few. We’ll go into more detail about those soon.

How do they work?

Every filter and most purifiers have an internal element or cartridge that has microscopic pores to catch debris, protozoa, and bacteria. In time, strained matter can clog the element’s pores so they do need to be cleaned regularly and eventually replaced.

Many purifiers use chemicals, like iodine, or ultraviolet light to kill viruses which are too small for filters.

The majority of filters and purifiers also have activated carbon in their elements because of its effectiveness at removing unpleasant tastes that come from things like leaf tannins. Activated carbon can also reduce contaminants such as pesticides and other industrial chemicals.


Before we get into all the different types of water filters and purifiers, I’d like to make a small note about prefilters.

Glacial sediment, silty water, and leaf and mud debris are all different factors that murk water in different ways. Natural particles impact how easy it is to treat water, how much field maintenance is required, and the lifespan of your filter elements.

Here’s where the prefilter comes in. It’s just an accessory that removes large particles from the water to improve the treatment process. All it does is make everything easier for you at the end of the day.

Pump-style products usually come with a prefilter, or one needs to be bought separately.

So, prefilters extend the life of the element, improve effectiveness, and help maintain a pump filter’s flow rate.

They are absolutely essential before using a UV purifier on murky water.

Types of Water Filters and Purifiers

Now we can finally delve into the many types of water filters and purifiers.

It is said that if you’re traveling within the U.S. and Canada then you should just need a filter and for other countries, a purifier is also needed.

This is because in the backcountries of the U.S. and Canada human traffic is relatively low, which is also why the main threats are only protozoa and bacteria. Where fewer humans are, the risk of viruses is also lower because of the way viruses are primarily transferred. Hence why only a filter is usually needed.

As local backcountries are starting to see a rise in traffic, it’s possible that a purifier may become necessary even in the U.S. though.

However, I would argue that it completely depends where you plan to go on your trip, and not so much which country you’re in. Obviously, in less developed countries the risk is higher. Consider the following;

If you know there’ll only be lakes nearby you should just need a purifier, whereas if you’re nearby mountains, you’ll probably need a purifier but not a filter.

My general rule of thumb is to always carry both a purifier and a filter. There is absolutely no reason not to use both.

Pump Filters and Purifiers

These mainly consist of a pump and a pipe. You simply place the intake hose into the source of water and then work the pump. Some products thread directly into a water bottle.

Pump mechanisms differ, as well as flow rates, so you need to choose whatever is best for your needs.

They are really easy to use, and generally easy to maintain in the field too. The internal element or cartridge is replaceable, and if it gets clogged you can just backwash it.

You are in control of exactly how much water you want to filter, but you will need to clean the element during your trip.

There are only three downsides to a filter/purifier like this.

Firstly, pumping can get difficult after a while and annoying. Also, if you need to treat a large quantity of water it would take quite long, and they are a bit heavier and bulkier than some other forms of water treatment.

Gravity Filters and Purifiers

Gravity filters and purifiers work with a two-bag system. You fill one bag with dirty water and hang it.  Then the water gets pulled down through a tube, through the filter, and then into the clean bag.

Most products come complete with two reservoirs and an inline filter, though the exact setup can vary.

These are great because, as the name suggests, gravity does all of the work for you making it super easy to use. They’re also perfect for group campers because they can handle large quantities of water at a time.

You can replace the element or cartridge, so they aren’t difficult to maintain in the field.

The thing is, though, you have to find a suitable place to hang the bags. Keep this in mind.

Unlike pump filters where you can gather water from really small seepages, with gravity filters you need to have access to something like a small stream. This is so that you are able to put the bag in and gather water. If you don’t have anything like that near you, it can be a challenge to use this one.

There’s also the waiting time. This treatment process is slower than pumping, but when camping this isn’t really a big issue. Gravity filters come in handy especially when you need a bunch of water to cook something.

UV Purifiers

These are pen-like devices, which have ultraviolet light at one end that you simply stick in your water bottle, push a button, and stir. This usually takes about 60 seconds, the light turning off by itself to indicate when ready.

The UV light neutralizes anything in the water such as bacteria, protozoa, and viruses.

They are very small, lightweight, and incredibly easy to use. Plus, you never need to clean or replace the element. Batteries are required though, so keep a couple of extra ones on you.

The only negative is that you can only purify a small amount of water at once, like just what’s in your water bottle. Which is why it’s better suited for hiking.

This is not a filter, it does not neutralize against dirt – it just kills anything in the water, so you do need a prefilter.

Drink-Through Filters

Drink-through filters and purifiers cover a wide range of different products. Essentially, the way that they work, is you’ll have something to fill and drink through, such as a bag with a filter in the cap. Or there are straw-style filters that allow you to drink straight from the source.

These types of filters are very compact, easy to use, and lightweight. It’s also a really fast method of water treatment. The only thing is, they cannot filter large quantities, making them perfect for hikes and not very useful when camping.

Let’s get into the different types.

Bottle Filters and Purifiers

These are bottles with built-in filtration and purification elements. Simply fill and drink.

Every single one is not exactly the same, for example, some use UV light.

This one can only treat a small amount of water, and the element needs to be cleaned in the field.

They’re great because they treat water quickly, the element or cartridge is replaceable, and they’re usually lighter and cheaper than pump and gravity filters.  

Squeeze Filters

These also come in a wide variety but, like bottle filters, you just fill and drink.

The difference with these is that you’re squeezing the water from the small reservoir to go through the filtration, and then directly into your mouth.

The element or cartridge is replaceable, so this is another one that is easy to maintain. It treats water very quickly, and they’re also generally lighter and cheaper than pump and gravity filters.

Some even double as gravity filters or straw-style filters.

You do need to clean it in the field, and the amount of water it can treat is limited to the size of a small bottle/reservoir/flask.

Straw-style filters

Straw-style filters let you drink directly from the source, instantly, and they are usually cheaper than pump and gravity filters.

Of course, this means that it’s just for one person so maybe best for one-man hikes, and if you don’t find a water source on your way then that’s a problem.

You do need to clean it in the field, and not all models have replaceable elements.

Chemical Treatment

There are many different types of chemical treatments, but the main ones are chlorine-based or iodine-based treatments.

All you need to do is drop the tablets or drops into your water, stir, and wait. They’re really small, lightweight, and inexpensive

Chemical treatment is a great back-up option to carry, even if you have another form of treatment.

When using chemical treatment though, you have to wait somewhere between 30 minutes to 4 hours for your water to be potable. This isn’t so great. The temperature of the water can affect how long it takes.

Iodine leaves a sort of metallic taste behind, but there are things you can add to your water, in addition to the iodine, to neutralize that taste.

Also, it doesn’t treat against cryptosporidium, which are protozoan parasites, and it’s not a good option for pregnant women or anyone with thyroid conditions.

Having said that, do whatever is best for you but be aware of any precautions like the ones I’ve just mentioned.


Water filters and purifiers are essential to not get sick while on your adventure.

If you choose not to be cautious about the water you drink while hiking or camping, there are so many diseases you could potentially get.

There’s no practical way to know if water is safe to drink, so it’s better to just treat it and be safe than to risk anything.

WHO provide a list of Waterborne Diseases that you could get from drinking untreated water from all over the world. Some of the diseases include Hepatitis A, Typhoid, Polio, Botulism, etc.

Simply put, using filters and/or purifiers could prevent you from getting a horrible disease and they keep you safe.

Just keep in mind that some waterborne pathogens can also occur from using contaminated water to cook or wash.

A study was conducted regarding the risk of giardiasis from the consumption of wilderness water in North America, and it was concluded that the infections are more likely caused by poor hygiene rather than contaminated water. It would be best to always keep hand sanitizer on you whenever you go camping or hiking. For more information you can read more at REI.

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