When you buy a water filter, the filter’s expiry date isn’t always obvious. You might know how long the filters last when they’re being used – but what about if the filter hasn’t been used?
The quick answer is yes, all water filters expire eventually. The filter material and quality, the brand, and whether or not you’ve used the filter will all determine its shelf life.
This guide will look at what it means for a water filter to expire, the health risks of using expired water filters, the factors that affect a filter’s lifespan, and more.
Table of Contents
💧 Do Unused Water Filters Expire?
Do water filters expire if you’ve never used them before? No. Generally, unused water filters do not expire. But that doesn’t necessarily mean you can keep them forever.
Many people bulk-buy their water filters and use them gradually over a period of months or years. This is fine to do, as most unused water filters have a shelf life of several years, as long as they don’t get wet.
However, I wouldn’t advise using water filters that have been stored for a particularly long time, like a decade. Natural degradation may have occurred by this point. Plus, the filter manufacturers typically release new, better filters or change their products after the five-year mark, so your filter may not be much good beyond then.
In short, it’s difficult to say exactly how long unused water filters last, because it’s rare for a manufacturer to share this information. If you do want to bulk-buy filters, I wouldn’t recommend buying more than three years’ worth of filters in advance.
📅 How is the Expiration Date of a Water Filter Determined?
We know that manufacturers don’t determine an expiration date for unused filters. But for used filters, manufacturers will give you an estimated lifespan for the filter. This is calculated through testing.
Before releasing a filtration product to customers, manufacturers will run extensive tests on the filters, determining what the filters can remove, and how many gallons of water the filters can effectively remove these contaminants from. This is known as filter capacity.
The capacity of a filtration system is how much water can flow through the system before the filter media becomes too clogged with contaminants to continue its performance.
For instance, an activated carbon filter uses adsorption to grab onto contaminants that affect water’s taste and quality. The filter media will continue to hold onto these contaminants, and the accumulation of impurities on the surface eventually leaves very little space for water to pass through. When this happens, the filter reaches the end of its lifespan.
🩺 Potential Health Risks When a Used Filter Expires
Using an expired used filter doesn’t only have disadvantages related to the speed and quality of filtration. The harmful contaminants trapped in the filter will, over time, thrive in the moist environment of the filter media.
Bacteria growth is also common in expired filters. While this might not noticeably affect your water’s taste or appearance, you could end up drinking harmful microorganisms that make you sick.
An old filter might even start letting contaminants through the media, or release some of the contaminants trapped in the media, if the pores become damaged and enlarged. As a result, you could end up drinking water containing a large quantity of chlorine, as well as bacteria, chemicals, and heavy metals.
Not all filtering cartridges have the same potential health risks within the same period of time. The lifespan of a cartridge determines when the cartridge will become unsafe to use, and when it needs to be replaced.
〽️ What Reduces the Lifespan of a Filter?
If a water filter has a lifespan of six months, there’s no guarantee that it will actually last this long. Six months is just a benchmark based on average water use and quality.
The four factors that affect filter life are:
The quantity of contaminants in your water affects how long a filter will last. If you run relatively clean water through an activated carbon filter, fewer contaminants will become trapped in the filter media. On the other hand, heavily-contaminated water will result in a faster buildup of contaminants in the filter media, reducing the surface area available and causing the filter to expire faster.
Common tap water contaminants like chlorine, hardness minerals, and heavy metals can clog filter media and affect its lifespan.
The number of people in your family, or how often you’re at home to use your water, will affect your water usage. This, in turn, affects a filter’s lifespan.
Let’s say a filter is designed to last for 40 gallons, or two months (like the Brita Standard filter). If you use more than 40 gallons within two months, the filter will last for less time. On the other hand, if you use less than 40 gallons within two months, you might get a few more weeks of use out of the filter before it expires.
I’ve used activated carbon as an example in this guide, as this is the most common filter material available today. But there are many other types of filter media, each with their own lifespans.
Ion exchange, carbon block, ceramic, mechanical, and nanofiltration are just a few filter types available today. Each filter has its own unique performance, and this determines how long the filter lasts.
Type of Filter
The most popular water filter is the drinking water pitcher, but there are also faucet and countertop filters, reverse osmosis filters, whole-home filters, backpacking filtering bottles, and under-counter filters.
Different types of filters have different lifespans, based on their size, install locations, and materials. For instance, under-sink filters typically have a lifespan of six months to a year, while smaller pitcher filters have life spans of up to 3 months, and backpacking filters can last for up to six years.
🔎 Signs That Your Filter Has Expired
There are several signs that your activated carbon filter has reached the end of its lifespan, and requires a replacement. These include:
Filter Change Indicators
If your water filter comes with a filter change indicator, the light will change color to indicate that the filter needs to be changed. Some filter change indicators work on a traffic light system, so you can buy a new filter when the light turns orange, as you know it’s nearly time for a replacement.
Most filter change indicators will change color based on timings, so if you notice other signs that your filter life has expired before your light turns red, you should go ahead and replace the filters early.
Change in Water Taste or Smell
The role of a water filter is to improve the taste and smell of your drinking water – so if your water starts to taste or smell unpleasant, it could be a sign that you need to replace your water filter.
You can quickly get used to the taste of clean water. If your tap water no longer tastes clean, consider how long it was since you last changed your filter.
Change in Flow Rate
Flow rate is one of the biggest indications that you need a replacement water filter. Most water filters will affect the flow of water in your house somewhat. But you’ll get used to the “new normal” flow rate, and if flow rate drops significantly beneath this, you know that it’s time to buy a filter replacement.
The same goes for flow rate in an activated carbon water pitcher. The flow rate of a gravity filter is slower than the flow rate from your kitchen faucet, but filtration will get much slower when the water filter has expired. I recommend timing your first few times filtering water through the pitcher and getting an average of how long it takes to filter a full jug. You can then compare this average time to future filtration times to determine whether your filter life has come to an end.
💬 Frequently Asked Questions
What counts as a used filter?
A used filter is anything that has come into contact with water. So, whether you use your filter every day, or you only use it at work or in a vacation home, the moment the filter touches water, it becomes used.
You should replace your filter as recommended by the manufacturer regardless of how often you use it. This is because, once the filter becomes wet, it becomes vulnerable to bacteria growth. Drinking bacteria can make you sick, and getting sick from your water would go against the purpose of using a filtered water solution.
What is the average filter capacity?
It all depends on the type of filtration system in question. Cartridges from the best filtration pitchers can last upwards of 150 gallons, while some countertop units have much higher capacities, reaching 3,000 gallons.
What’s the shelf life of Brita filters?
There are several Brita filtering products, including the Brita Standard filter and the Brita LongLast filter. The Brita Standard has a 2-month lifespan, while the Brita LongLast has a 6-month lifespan.
What are the benefits of replacing a filtering cartridge?
Aside from knowing that your water is free from bacteria, chemicals, and other dangerous contaminants, getting your cartridges replaced on time will ensure your water pressure is consistently high, and that your water always tastes and smells at its best.
Is it easy to replace a filter?
Usually, yes. The best drinking water systems house filter cartridges in a unit that the cartridges can easily be removed from when replacements are needed. Some systems have twist-on filter cartridges, while in others, filters come in and out of the unit by clicking and pushing. Replacing a water filter doesn’t typically require any tools or major work on your part.
What’s the difference between lifespan in months and lifespan in gallons?
A filtering cartridge’s actual lifespan is how many gallons of water it can treat before it needs to be replaced, as determined by the manufacturer’s testing.
The lifespan in months is how many months the cartridge is expected to last based on the number of gallons filtered.
While the number of months is more of a rough estimate, the number of gallons is much more accurate.
What happens to old filter cartridges?
Some manufacturers have schemes where you can save your old filter cartridges and return them for a perk (such as a free filter). Many filtered water systems now offer recyclable cartridges, so even if the manufacturer doesn’t have a recycling scheme, you can still recycle old cartridges with plastics when you’re replacing them with new ones.