Do Chlorine Tablets Expire? (How Long Do Most Last)

When it comes to your pool, chlorine is a very important part of keeping your water safe and clean for you and your guests. Chlorine tablets are one of the most popular forms of chlorine treatments because of how easy they are to use. 

Chlorine tablets do expire. While all pool chemicals will expire eventually, most chlorine tablets last for 3-5 years with proper storage. Chlorine tablets should be stored in a cool, dry, and dark place to stay usable for longer. When kept in the right environment, pool chemicals can last for over five years.

Pool chemicals should be able to last you many years, but simple mistakes when it comes to how you store your chemicals can make them expire prematurely. Today we will be breaking down how you should store your chlorine tablets and how to know if they have expired.

How Long Do Chlorine Tablets Last?

Chlorine tabs have a shelf life of three to five years. Compared to other chlorine options, chlorine tablets, also known as Trichlor tablets, last much longer. 

Normal Shelf Life 

The shelf life of chlorine tablets varies slightly by brand, but it usually lasts between three and five years. If the chlorine tabs are stored correctly, they could last for over five years. Storing your chemicals correctly means that you are keeping them in a dark, dry, and cool place. 

Chlorine Tablets

Failure to adequately store your chlorine tabs will result in a much shorter shelf life for the chemicals. The worst thing about chlorine tablets is moisture so your chlorine tabs will quickly expire if you do not have their packaging sealed tightly.

Every brand will have a different recommendation for their products’ shelf life but none of these expiration dates are definitive. How long your chlorine tablets last is based mainly on how they are stored and how they are protected against the outside environment.

Expiration Dates by Brand

Brand of chlorineType of Chlorine*Shelf Life
Clorox3″ Chlorinating Tablets3 years
Chloro-Guard Liquid Chlorine6 months
Pool Mate Chlorine Granules5 years
In the Swim3″ Chlorinating Tablets5 years
HTM1″ Chlorinating Tablets5 years

*Note that the type of Chlorine plays a large part in how long the Chlorine lasts on the shelf.  Manufacturers may produce other types of chlorine that last more or less time.

Signs the tablet has expired 

Knowing when your chlorine tabs have expired can be a tricky thing. Not all chlorine tabs will last the same amount of time so you cannot know if they are expired just based on an expiration date. There are some signs that you can look for that will help you indicate if your tablets have expired.

One of the tell-tale signs that your chlorine tabs have expired is the smell. If your chlorine tabs smell strongly of chlorine or bleach, that is a strong indicator that your tablets have expired

How To Make Chlorine Tablets Last Longer

There are many things that you can do to help your chlorine tablets last as long as possible, such as keeping them in a dry, cool place with no light. The reason that chlorine tablets have a longer shelf life than liquid chlorine is that dryness helps preserve the chemicals for longer. 

Chlorine tablets should stay as dry as possible. This means that you need to make sure that your container is tightly sealed at all times, preferably with a bucket lid. This step is especially important if you live in a humid place. 

Chlorine tabs should be kept in cool places. The ideal temperature for storage is between 50 and 70 degrees Fahrenheit. Any large jumps in temperature aren’t great for the chlorine tabs either.

It is also important to keep your chlorine tabs in a dark place. The sun’s UV rays hurt chlorine and can tamper with the product. This also means that the tub you keep your chlorine tabs in needs to be opaque. 

Pool beside the house

I would recommend that you keep your chlorine tablets in a well-ventilated place. A well-ventilated area will keep you safe so that the chemical fumes do not float around and become overwhelming. If you follow these recommendations, your product will last many years.

To summarize, it is essential to keep your product in a place that is cool, dark, and dry. If your chlorine tabs get prematurely wet or moist, they will begin to dissolve and break apart. If chlorine taps become too hot, they will degrade and lose their potency. 

If these steps are followed, your chlorine tabs can retain their potency for a minimum of three years. These conditions are usually standard for all pool chemicals. It is a smart idea to find a location for you to store your chemicals before you start using your pool.

Signs The Tablet Has Expired

If your chlorine tablet looks or smells differently than it should, it has likely expired.  It is important to know the signs of an expired chlorine tablet. Because their expiration dates are more of a guideline than a set date, you will need to be able to determine on your own if your chlorine tabs are expired. 

The first big thing to look for is any odd smell or odor. Something you do not want to be smelling is the smell of pool chlorine or bleach. If you are smelling chlorine, that means that chlorine is leaving your tablets. Once the chlorine has left the tablets, the potency of the product will go down and they will no longer work to their full extent. 

Chlorine tablet on pool

The second major thing to look for is any discoloration in your chlorine tablets, The tabs should be stark white. If this begins to fade or change hues, your chlorine tabs are probably expired. 

Make sure that the tablets look well-formed and in good condition. If the tablets become misshapen and break apart, this could be an indicator that your storage was not good enough. If you know that your chlorine tabs are not being properly stored and have been overheated, exposed to moisture, or in the sun, you might want to replace your tabs. 

What Happens If You Use Expired Chlorine Tablets 

If you use expired chlorine tablets you will not get the results you are looking for. The older your chlorine tablets are, the less effective they will work. 

Chlorine leaves the tablets over time which takes away the cleaning power of the tablets. If properly stored, your tablets could still have a large percentage of chlorine in them even after years. You can tell they are in good condition if they have no smell and remain a starchy white color.

Eventually, the chlorine will leave the tablets entirely and the tablets will not clean your water at all. If you notice your tablets smelling bad or becoming discolored, they are most likely unusable and will not clean your pool. 


Using an expired chlorine tablet is not dangerous and there will be no harm done to your pool. There will most likely be no reaction at all to the water. 

The largest danger would be that your pool is not being cleaned and it would be unsafe to swim in. If you use expired chlorine tabs and don’t realize it, you will be swimming in unchlorinated water. 

Improper Storage For Chlorine Tablets

Most people do not realize that chlorine tablets cannot be stored in extreme temperatures or with poor ventilation. Pool chemicals are dangerous and should be treated with a lot of caution and care. Storing them badly not only damages the product and wastes your money, but it also can lead to some hazardous incidents. 

Overheating and Underheating

Pool chemicals are not meant to be put in any extreme temperatures. They will not react well if they are too hot or too cold

If you leave your chlorine tablets in a place that is too hot, they will begin to release gas and expand inside their container. If the pressure becomes too much, they will explode their container. 

An exploding container of a chemical is never safe, especially when it could potentially mix with other chemicals around it and create a dangerous reaction. In extreme cases, these explosions can lead to fires. Chemical fires are extremely dangerous and can be very catastrophic. 

Lack of Ventilation 

Another danger that can happen when you improperly store pool chemicals occurs if you do not store them in a ventilated area. Ventilation is necessary for places where you store any of your pool chemicals.

Without proper ventilation, these chemicals will give off toxic fumes and vapors and can plague the air. These chemicals can corrode metals and rust nearby items. This can cause much damage to your property that could have been easily avoided. 

Unsafe Pool Water

Storing your chemicals wrong also makes them ineffective faster. Using ineffective chemicals in your pool will make it a breeding ground for dangerous bacteria and algae. Chlorine is an essential part of maintaining a safe and clean swimming pool and using improperly stored chlorine tabs takes away the sanitizing powers of chlorine. 

Best storage containers for chlorine tablets

An airtight container is preferred to make sure that no water can get in. Water can prematurely spoil your entire batch of chlorine tablets. A good container in a cool, dark, and dry space is your best bet to keep your product fresh. 

Storing your chlorine tablets in a proper container is very important and will help keep you safe and make your product last longer. A lot of chlorine tablets come in containers that are suitable and will protect your product well.

Look for containers that have a secure snap-on or press-on lid. Any type of zip lock bag will not do the trick. Some brands also offer individual packaging for each unit which gives you extra protection. 

If you feel that the container that came with your chlorine tablets is not good enough, go to your local hardware store and buy a large bucket with a secure lid. These will do a great job of keeping your product fresh.

Something to consider in choosing a storage container is picking one that is opaque for an extra layer of protection from UV rays. You should still keep these buckets in a dark place. 

Hopefully, this information will help you chlorinate your pool properly!

Leave a Comment