Do Pool Chemicals Expire?

Many pool and spa owners like to buy pool chemicals in bulk. In general, this is a good practice: it helps keep costs down and ensures that there's a regular supply on hand for maintenance. However, it's important to be aware that while most pool chemicals stay fully effective for a long time, some become ineffective in a shorter time period. Thus, it may be more beneficial to purchase certain chemicals on an as-needed basis. Which pool chemicals last and which ones do you need to worry about?

Do Pool Chemicals Have a Shelf Life?

All pool chemicals do have a shelf life, but for some, the shelf life is so long that most people will use up the chemicals they buy long before they expire. This depends on the specific product, however. Some pool chemicals expire in a much shorter window. It's important to learn which products belong in each category and to keep an eye on the expiration dates of chemicals that are likely to expire before you run out of them.

As a general rule, liquid acids and dry pool chemicals can last for several years if they're properly stored away from heat and moisture while most chemicals in liquid form have a shorter expiration date. For example, granular chlorine has a long shelf life, but chlorine in liquid form does not. So if you buy liquid shock, be aware that it only lasts one to two months at the most before it starts to lose effectiveness.

While many swimming pool chemicals stay good for years if stored correctly, some pool-maintenance supplies expire more quickly. In particular, the test strips and reagents you use to check your pool's water chemistry will expire after one to two years depending on the brand. Old test reagents and strips can give inaccurate results if you use them for testing the water, so these should be replaced before they hit their expiration date. For example, if you have some of these supplies left over after winterizing your pool, it may be better to discard them and buy new test equipment when you reopen the pool.

How to Store Pool Chemicals Correctly

The best way to make sure your pool chemicals stay fully effective is to store them properly. Generally, this means separating liquid from solid chemicals and separating acids from other chemicals. This prevents chemicals from losing effectiveness, and from reacting with one another in hazardous ways.

Additionally, chemicals for your pool should be stored somewhere cool to prevent loss of chemical effectiveness due to heat exposure. The best storage area is one that doesn't get hotter than 85 to 95 degrees or cooler than 36 to 40 degrees. Your chemical storage area should also be dry and well-ventilated to prevent gas buildup, and to prevent solid chemicals reacting with water.

Test strips and reagents should be stored at 36 to 85 degrees, and out of direct sunlight. If possible, they should be kept somewhere cool or temperature controlled, such as an indoor cupboard or closet located near an air-conditioning outlet.

Safe Pool Chemical Disposal

To dispose of your unwanted pool chemicals safely, treat them like household hazardous waste and take them to a local HHW disposal facility. Never put these chemicals out with the trash or pour them on the ground, down a home drain or toilet, or into a storm drain. Instead, call your nearest waste-management agency to find out when and where you can drop these chemicals off so that they can be handled properly.