How Long Do Unused Water Filters Last? + Tips & Tricks

Drinking from wild water sources can be dangerous. Therefore, it is important to use water filters when hiking, but how long do they last?

Here’s how long unused water filters last

Rule of thumb answers range between 300 to 500 gallons, and six months to a year, depending on the frequency of usage. But it also depends on the kind of filter used.


What are water filters?

Keeping hydrated is vitally important when hiking, whether you’re just taking a day trip, or undertaking a journey of hundreds of miles over an entire month. With day trips, it is easy enough to pack your rucksack with water supplies from home. However, on an extended trip, locating regular water sources becomes a key part of planning. Whilst drinking from certain mountain streams used to be considered relatively risk-free at higher altitudes (Ben Nevis’s Red Burn in Scotland, for instance), official advice now urges using some form of water purifier.

Survivalists say you can take a chance on rushing water, as opposed to ponds and pools, but why take the chance? There can be very unpleasant things lurking in wild water sources.

Boiling water kills harmful bacteria and eliminates dangerous pathogens. However, simply boiling doesn’t remove all nasty elements that could harm your body. Getting sick on the trail, potentially miles from civilization, is no joke. It is therefore all but essential to undertake some means of purifying, ideally using water filters.

Water filters come in a variety of forms, making it easier to drink safely from wild water sources. They can be purchased relatively inexpensively, and can last for a good long time, but not indefinitely. They operate on the principle of physically blocking larger particles from the water by running it over a substrate barrier. With repeated use, the filter clogs up, and the water flows less easily.

How do you know when your used water filter has expired?

The easiest way of telling when a water filter needs replacing is when the flow of water slows, and it becomes difficult to drink through. They typically need replacing every three to six years, on average, depending on use, and on the kind of water being filtered. For instance, muddy water or water with silt will end up clogging the filter more.

On paper, it might look like hikers seldom need to replace their water filters. After all, using up a 300 to 500-gallon lifespan means using the filter weekly for about five years. However, filters can get brittle with age and repeated use. Also, cracked filters (normally caused by the freeze and thaw cycle, but accidental damage can occur as well) should not be used, as the substrate barrier is compromised, and unfiltered water can flow through, bypassing the filtration system.

The expiration date for used water filters

A variety of factors can affect the life span of a water filter. Regardless of how long manufacturers claim they last, it is very hard to be certain about, considering their measurements are based on continuous flow out of a tap, rather than backcountry water supplies.

Backpacking water filters are advertised to churn through between 300 and 500 gallons, on average, though some manufacturers make inflated claims of being able to last 100,000 gallons. The key factor is the water source, and how much care and maintenance is applied to the filter. They can also get brittle with age and repeated use.

It also depends on the kinds of water filters you use. Here are some examples.

Carbon Filters

These remove contaminants via absorption. They can also remove bad smells and tastes due to their large, porous surface area. Most importantly, they remove bad particles. However, these are not as durable as other filters, and typically require replacement after six months to a year at most.

Ceramic Filters

These are similar to carbon filters and eliminate the most harmful microbes, bacteria, and other nasties. For a bug to do any damage, it would need to be smaller than a micron to stand a chance of getting through a ceramic filter. I’ve no idea how small a micron is, but 99 percent of the harmful nasties are bigger than that.

In short, ceramic filters are a great way to go, even if they are a bit more expensive. They average between 100 and 200 cleanings before water can no longer be properly filtered. Typically they need replacing at around six to eight months.

Press Filters

These are similar to other filters, but often easier to use, and normally come in bottle form. They operate on a push method system, putting the water through four filtrations before it enters the mouth.

Expiration dates vary, with 60 to 70 gallons being a good average for usage. Some of these can be sold with stand-alone filter cartridges that attach to bottles, so making a purchase of this kind can potentially save money.

Gravity Filters

These look like paraphernalia seen in hospitals used in IV treatments. Gravity Filters work on a similar principle, by using – you’ve guessed it – gravity. They have a straw instead of a needle, and the bags are different too, given that one filters water and the other does not. But in other respects, the system is identical.

The filtration is as good as any other, but these can need replacing every couple of months. However, that is only if they are in constant use, as they can filter up to 500 gallons.

Lifestraw and Crazy Cap Filters

These are popular, but not as effective as other filters. Lifestraw does filter out quite a lot of harmful microbes, but some can still get through. Crazy Cap uses ultra-violet light to kill bacteria, but again, this isn’t 100 percent effective.

Crazy Cap’s expiration depends on the life of the UV light used for filtration. Lifestraws can last for a few years.


Water purifying tablets can be very handy. There are several brands out there, available at relatively cheap costs. However, they only work for one cleaning, typically one liter per tablet. They can also expire quite quickly, once a packet is opened, so that’s worth bearing in mind.

How do you store water filters?

It is best to store water filters on shelves in a closet at room temperature. Extremes of temperature can damage the filters. Therefore it is vitually important, when travelling, to carefully inspect filters for cracking that can occur if it has frozen and thawed. In such circumstances, it is better to switch to water purifying tablets as an emergency second option.

Is it safe to drink using expired unused water filters?

It depends on what kind of filter. As mentioned above, water purifying tablets need to be used quickly once the packet is opened, or they are ineffective. The freeze and thaw cycle can damage other filters listed above, so good storage is important.

How long do water filters last in storage?

An unused filter that’s simply sitting on a shelf won’t need replacing, provided it isn’t being stored in extreme temperatures. Shelf life versus use life is different things, however, so no matter how carefully you store a water filter between hiking trips, it is worth bearing in mind the wear and tear factors discussed above.


When it comes to the wise use of water filters, it is important to bear manufacturer specifications in mind. Expiration dates can vary, as explained above, depending on how often a filter is used. However, it is also noting that some manufacturer guidelines can exaggerate in terms of how long it takes for a filter to fall into disrepair. Common sense should be the ultimate deciding factor, given that a clogged filter will inhibit drinking, and cracked or otherwise impaired filters will visibly display damage.