Types of Hiking Filters
Structurally, there are three main types of hiking microfilters:
Pump filters.
Gravity filters.
Flow filters.
Hiking pump filters. In these filters, you pump the water yourself using a pump.
Advantages of Pump Filters
You can filter exactly as much water as you need — for example, just a couple of sips. Typically, pump filters have a fairly long intake hose, allowing you to draw water from shallow or hard-to-reach bodies of water where it is difficult to scoop it out. For example, from a puddle or a stream with steep or crumbling banks.
At the end of the hose, there is usually a pre-filter to clean the water beforehand. It strains the water, preventing large impurities from entering the hoses and clogging the cartridge.
The hose often has a float, allowing the intake to occur from the upper, usually cleanest edge of the water.
A pump filter allows you to draw water even from a shallow body of water where it is inconvenient or impossible to scoop it. You can attach a float and pre-filter to the hose — the float will prevent debris from being sucked in from the bottom, while the pre-filter will clean the water at the inlet from sand and larger debris.
The speed of water passing through the filter cartridge depends on the material it is made of, as well as the design of the pump itself. For example, water passes through the MSR MiniWorks and MSR TrailShot filters at the same speed of 1 liter per minute, but the MiniWorks has a ceramic cartridge and a powerful pump with a long lever, while the TrailShot has a hollow fiber cartridge, but a "squeeze" pump that fits in your fist and is pumped like a hand expander.
The claimed working speed of pump filters ranges from 1 to 3 liters per minute. But this is provided that the cartridge is clean and has not clogged with fine debris, and the user is actively pumping water. In real conditions, the flow rate can drop by 2-2.5 times.
Disadvantages of Pump Filters
You need to pump the water. Sometimes this requires considerable effort, especially when filtering a large volume of murky water that constantly clogs the cartridge. You cannot step away — you have to stand by the water source and monotonously pump the water. The pump has many moving parts that need maintenance — changing gaskets, lubricating the handle, and so on.
Weight — all else being equal, pump filters are heavier than other designs. For example, the compact gravity filter Platypus GravityWorks 2L weighs only 187 grams, while the comparable MSR HyperFlow, which filters at the same speed, weighs 221 grams.
Examples of pump filters: MSR SweetWater, MSR HyperFlow, Katadyn Pocket, Katadyn Combi, and others.
Hiking Gravity Filters
Here, all the work of filtering is done by gravity. A container with dirty water is hung higher, and the filter cartridge is built directly into it or into the tube. Water flows down this tube, is filtered in the cartridge, and, once clean, fills the bottle or bladder.
Gravity filters are communicating vessels, with the filter cartridge located between them. To purify the water, you only need to place the container with dirty water higher than the container with clean water.
Advantages of Gravity Filters
They do not require the user's presence — just hang the container with the water being filtered, and you can rest or set up camp.
Gravity filters work quickly — they purify an average of 1.5 liters of water per minute if the cartridge is not clogged. You do not need to pump the water, so you can comfortably filter large volumes — from 2-3 to 10 liters at a time.
Gravity filters are reliable: there is practically nothing to break due to their simple design.
In terms of the "weight/volume" ratio of filtered water, they have no equal. The MSR AutoFlow XL weighs only 340 grams but is equipped with a 10-liter bag, which it can filter water from in about 6-7 minutes.
Disadvantages of Gravity Filters
It is inconvenient to quickly filter small volumes of water: for a single cup of clean water, you need to open the container, pour in the water, connect the filter, and wait for the water to filter. You first need to collect water in the container, which can be difficult from shallow or hard-to-reach bodies of water.
Gravity filters do not have pre-filters on the dirty water containers. Therefore, if the water is heavily polluted, you need to strain it yourself first to remove large debris; otherwise, it will quickly clog the filter cartridge.
Examples of gravity filters: Platypus GravityWorks, MSR AutoFlow, Katadyn Camp, and others.
Flow Hiking Filters
This is a very diverse group of hiking filters that cannot be classified as either gravity or pump filters. They can vary significantly in design and properties, and can be conditionally divided into three classes.
Bottle filters. The filter cartridge is built into the neck of a soft flask. You fill it with dirty water, then squeeze or roll it to create the necessary pressure for filtration — the water will flow out of the neck already clean. The main advantage of such systems is their low weight. For example, the soft one-liter Katadyn BeFree flask with the filter weighs only 63 grams.
The Katadyn BeFree filter is built directly into the cap of the soft flask that comes with it. You squeeze the flask — the water is forced through the filter cartridge and is purified in the process.
Inline Hose Filters.
In the English-speaking world — in-line microfilters. As the name suggests, they are integrated into a break in the hose. This allows you to filter water from a tap or from a hydration system bag. If desired, such a filter can be turned into a gravity filter — you just need to securely connect it to a container for dirty water and hang it so that the water flows through the filter cartridge via the hose.
The MSR Thru-Link flow filter is integrated into a break in the tube of a hydration system. If you hang the hydration pack, the MSR Thru-Link will work like a gravity filter.
Filtering Straws.
You can drink directly from a water source, such as a puddle or pond. The most well-known are produced under the LifeStraw brand. Lightweight and compact, they are not very applicable in real hiking practice. With such a straw, you have to lean over the water's surface, where there may be dirt, and you cannot fill a flask or bladder for later use.
With the LifeStraw, you can drink directly from a puddle, but you won't be able to collect clean water.
Which Class of Filter to Choose?
Much depends on your preferences and experience. We will only provide guidelines based on established hiking practices:
Pump filters are suitable for solo hikers and small groups of up to three people. They are also the only choice if you often need to collect water from hard-to-reach or shallow sources — puddles, ponds with unstable banks, or streams between rocky crevices.
Gravity filters are suitable for small and large groups of hikers, as they can filter large volumes of water without human involvement — up to 10-15 liters at a time.
Flow filters and bottle filters are suitable for solo hikes and ultralight hikers due to their deceptively low weight.
Straw filters are only suitable as a means for individual water filtration in emergencies and are impractical in real hiking situations.
Lifespan of a Hiking Filter
Typically, responsible manufacturers indicate the amount of water that can be effectively filtered, after which the filter cartridge needs to be replaced. Even the most "short-lived" fiberglass filters can purify about 750 liters of water. But that’s quite a lot. A resource of 1000 liters is sufficient to, for example, hike the entire long Pacific Crest Trail, filtering 5 liters of water daily. This calculation is for 130 days, taking into account that due to murky water, the actual filter resource will be 20-30% lower than stated. This is usually enough for regular hikers for 3-4 seasons of cartridge use, with each season comprising 28 "field" days. More durable options should be considered if the filter will be used more intensively — more frequently or in highly polluted water with a lot of silt and fine debris.
The cartridge of most filters can be replaced with a new one when its resource is exhausted. Therefore, the availability of replacement cartridges is very important when choosing a new filter. If they are not available on the shelves, you will have a useless casing at home that cannot filter water. Also, pay attention to the cost of replacement cartridges and their lifespan. Sometimes, a complete filter costs less than competitors, but its cartridges are expensive and have a shorter lifespan. This can make its long-term maintenance more expensive, and it may be better to buy a filter model with a higher initial price but cheaper "consumables" right away.
Hiking Filter. Part - 2