Do Water Purification Tablets Expire?

Last Updated:

We all enjoy drinking clean water.  However, when you are out in nature or find yourself in an emergency, access to clean water can be a little hard to come by. That is why many people buy water purification tablets. The problem is, do you even remember when you purchased your purification tablets, and do they still work?

The most important question is, do water purification tablets expire? Most water purification tablets do expire. Of the two most used types of purification tablets, Aquatab expires after five years, while iodine-based tablets expire after six years. A few other tablets range in having shorter or slightly longer shelf lives.

While there are multiple ways to purify water, such as boiling it on your stovetop, water purification tablets are a typically faster and easier method to get clean water. Most purification tablets use two different types of chemicals, which can have different effects on the water cleaning and the body. While it is usually okay to use tablets shortly after their expiration date, below is more information on how tablets work and ways to avoid early expiration as well as when not to use the tablets.

How Water Purification Tablets Work

Water purification tablets are used to kill pathogens that are present in water in nature that are dangerous for humans to consume. By using iodine, chlorine, or chlorine dioxide, water from a mountain stream or water that has been contaminated by natural disasters can be rid of harmful bacteria and viruses. The chemicals work to deactivate the microorganisms, making it safe to drink the water they are in. 

Most tablets work by putting them in the water and letting the tablets dissolve. Most tablets on the market require the tablets to sit in the water for thirty minutes or more. While tablets purify the water, many may leave an unpleasant aftertaste. 

For iodine tablets, you can buy iodine neutralizer tablets (REI Products) that can neutralize the taste, so you feel like you are drinking healthy water. For the chlorine tablets, you can leave the container open, and the chlorine will evaporate, allowing the water taste to return to normal.

Water purification tablets are usually a preferred method for water purification because the tablets are light and don’t require any particular kind of equipment to use; this is why many emergency kits use them. Unlike boiling water and using water filters, water purification tablets take up less space and are an immediate purification method if the tablets are properly stored.

How Purification Tablets Stop Working

Like most non-reusable products, water purification tablets can stop working if not taken care of properly. Multiple factors, including nature, can lead to a water purification tablet being ineffective.

Natural Expiration

As chemicals sit in a state of non-use, the compounds slowly start degrading. This degradation leads to the substances being ineffective in deactivating the pathogens in the water; this is commonly known as expiration.  Many tablets have natural expiration dates years from the date they are produced.

Elemental Exposure

The chemical makeup of water purification tablets can be sensitive. Exposure to various natural elements can cause the water purification tablet to stop working before the expiration date. 

  • Heat exposure: Exposure to extreme heat causes the chemicals in the purification tablet to degrade at a faster pace than usual. The quicker degradation means that the tablets will expire and be ineffective earlier than anticipated. 
  • Moisture: If The purification tablet is exposed to water before use, the chemicals will also start to degrade faster, leading to an ineffective tablet. 
  • Sunlight: The heat from the sun can stimulate the chemicals, leading to faster degradation an expiration of the tablet. 
  • Air Exposure: Exposure to the air also causes the tablets to become ineffective faster; this is why purification tablets that are individually packaged tend to still be effective and last longer than tablets kept in a bottle. Frequent exposure to air can also allow the tablets to become contaminated from outside pollutants. For this same reason, you should refrain from opening a purification tablet pouch before you plan on using the tablet.
  • Humidity: While the water might not be directly touching the tablets, the temperature, along with the higher amount of water in the air can cause the chemicals to become unstable, leading to an ineffective purification tablet.

Improper Storage

The improper storage of purification tablets could range from not closing the lid tightly to losing track of them and not knowing where they have been. Improper storage of the water purification tablets can both make the tablets ineffective and potentially pose a risk to you if you want to use the tablet.

Container Deterioration

Because purification tablets are so sensitive, it is vital to make sure the containers they are in are kept in top condition. If the lid of the container is not airtight or if the container starts to rust, the tablets will be contaminated and will not work to purify your water. 

is this safe to drink?

Are expired water purification tablets safe to use?

As we shared earlier, most purification tablets are composed of either chlorine or iodine. These chemicals degrade over time. After the expiration date posted on the tablet packaging passes, the chemical composition of the tablets is unknown; this means that it is impossible to say how effective the tablets will be at purifying your water. 

The chemicals in the tablet should not do your body any severe harm, but the pathogens in the unclean drinking supply may still be there, meaning you are not drinking pure water. Not drinking pure water could be hazardous to your health.

Some people try putting more than the recommended number of tablets in their water after the expiration date in hopes that the amount of chemical present will purify the water; this is a rather dangerous idea. While the chemicals have degraded, the number of chemicals entering your body could do damage to your system. It will be safer just to buy new purification tablets if the ones you have are already expired.

Checking for Expiration

What do you do if you have a bunch of water purification tablets, but you can’t find out their expiration date? If you really want to use them, there are a couple of tests you can do to see what the current effectiveness of the tablet is. 

Squeeze Test

Take one of the tablets between two of your fingers and squeeze on the tablet. If the tablet crumbles easily between your fingers, this means that the iodine or chlorine has degraded a lot. Such tablets are probably not usable.


This test applies only to iodine tablets. Iodine tablets are usually a brown or gray color. Tablets that are yellow or greenish have already progressed to a far state of degradation. These tablets are not usable and should be thrown away. It is always a good idea to do a color test before using a tablet.

These tests are especially helpful for purification tablets that are found in an open container. Once a container has been opened, the tablet will expire much faster, usually within a year after being opened. The only purification tablet that is known to not abide by these expiration rules is Polar Pure (Amazon), which uses crystallized iodine and is less like a tablet.

Final Thoughts

In short, most water purification tablets have expiration dates and are ineffective after expiration. While it might be safe to use the tablets for a couple of months after they expire, purification tablets are not that expensive. It would be safest just to buy some new tablets for your next hike.

About the author