Do Pool Chemicals Expire? How Long Can I Keep Pool Chemicals

In a perfect world, or if you’re as OC as some people around the office (shifty eyes looking around) you should only have enough pool chemicals to last you the entire season so that once the new season rolls in, you’ll have a new batch of pool chemicals that’s in their full potency. But in reality, one look at many pool sheds and you’ll find chemicals that are years past their prime. Either because of neglect, over-ordering, or just under-usage when we conveniently “forget” to clean and balance our pool.

What’s the shelf life of pool chemicals?

Different chemicals have different shelf lives. Today we’re going to go over your inventory of pool chemicals so we’ll know which ones are still good, which ones have gone bad, and how to store them for maximum shelf life.

Unstabilised Liquid Chlorine

Liquid Chlorine has the shortest shelf life of all your pool chemicals, losing up to 50% or half of its potency six months from when it was first opened and up to 90% after a year. If your liquid chlorine is exposed to sunlight or extreme temperatures (like what we have here in Australia) then this degradation happens a lot faster.

Pro Buying and Storage Tip: Only buy enough unstabilised liquid chlorine to last you the season and keep it in the darkest and coolest part of your storage shed. Also make sure that the lid is tightly sealed after using to avoid lowering of potency.

Granular Chlorine or Calcium Hypochlorite

Granular chlorine (also known as pool shock) is sold in 2 packaging types, in sacks/plastic bags or in those white plastic buckets. If you have a choice, go for the ones in white plastic buckets. The reason for this is that granular chlorine ca and will absorb moisture from the air, dissolving it. In fact, some people have reported that small tears in their granular chlorine bags have resulted in a pasty-unusable mush that’s basically unusable only after a couple of months. But if stored properly in air-tight containers, they have a shelf life of up to five years!

Pro buying and Storage Tip: Even though granular chlorine is pretty cheap, if you can get a great deal on it, then go for it. To prevent a whole batch from turning into mush, repack them in single dose Ziploc bags! Your actual volume may differ depending on the size of your pool but this is a great way to ensure that your granular chlorine stays viable for as long as possible. It’s convenient (just grab a bag when you need to shock your pool) and it prevents exposure of the rest of your granular chlorine to moisture. Just make sure to store your repacked bags of chlorine in a cool and dark place away from sunlight.

Chlorine Tablets

These are the most convenient forms of chlorine. Not only are they pre-dosed into tablets, but are a little more resilient than granular chlorine when it comes to exposure to moisture in the air. Just make sure to tightly close the lid of the container that they come in and they should be at their peak efficiency for three years and still viable for up to five years!

pH up and pH down Chemicals

These alkaline and acidic chemicals like hydrochloric acid can last for over five years, but we strongly suggest that you just get enough for one season and reorder a new batch the next season. The reason? Well, they’re corrosive. In their pure forms, they’ll probably last much longer than the containers that placed in! Chemicals that eat through their containers can pose a big problem when they spill over and mix with other chemicals in storage, causing toxic fumes or even a fire.

For a safer alternative, go for pH adjustment chemicals that are in their powdered or solid forms.

Alkalinity up and Calcium Up

These two pool chemicals are similar in both appearance and longevity. When stored properly, they can last for up to five years and they’re pretty much unaffected by temperatures so they’re perfectly safe to store in an outdoor shed, just make sure that their containers are tightly sealed. The only problem you’ll have with these chemicals in the long run is if they absorb moisture from the air and they start to clump together and cake, forming small, hard blocks of the substance that will be hard to measure and dissolve in your pool.


While algaecides are pretty shelf-stable and will be viable for up to five years, we only recommend getting enough to cover you for a season and a little bit for the off season. The reason for this is that lower temperatures will tend to affect the efficacy of algaecide or can even completely render it useless. Algaecide should also be stored away from direct sunlight and high temperatures.

Clarifiers and Flocculants

Much like algaecide, clarifiers and flocculants are pretty shelf-stable and are viable for up to five years, but care should be taken when storing them outside as extremely low and high temperatures can damage the product, making it a useless white powder or liquid.

Stabilizer or Cyanuric Acid or UV Blockout

Remember when they said that cyanuric acid lasts forever in your pool? Well, that’s true with the pure version of the chemical as well. Cyanuric acid can last almost indefinitely as long as it’s stored properly. Actually, even if it absorbs moisture from the air, it’s still very potent, just a bit messy to deal with. Make sure to properly label the bottle or container with “Cyanuric Acid” or whatever you need to remind yourself of the contents as the bottle label will be long gone before the contents will be.

TLDR (Too Long, Didn't Read) a.k.a. Conclusion

Did you read through all that? Or did you just skip over to this section? No matter. So here’s the summary that’s applicable to all pool chemicals and how to make sure that they’re all at full potency when it comes time to apply them.

  • All pool chemicals, aside from unstabilised liquid chlorine, are good for up to three to five years as long as they’re stored in a cool and dark place away from sunlight and they’re packed in air-tight containers.
  • Granular chlorine can be re-packed to extend its shelf life.
  • While buying bulk may sound like an attractive option, you’re actually losing money if the bulk of it has lost its potency due to improper storage and handling.
  • You’re still saving money if you use up all of your chemicals every season and you’ll get full potency with every new batch of pool chemicals.
  • These are all poisonous chemicals, so always wear proper protection when handling and always keep storage areas locked to prevent children from causing accidents.


For more information on the different types of pool chemicals, dosages, and other useful stuff, be sure to check out Mr Pool Man's Ultimate guide to pool chemicals.  

Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

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