Yes, hot tub chemicals can and will expire on average every 5 years. Expired water chemicals might not be as effective as newly produced water products, so make sure that you get new bottles before the old ones expire.

It is very important that we use hot tub chemicals in our hot tubs and it is even more important to keep an eye on their expiration date. Just like any other product or food, hot tub chemicals can expire. Having expired hot tub chemicals means that their efficiency in the water will be significantly reduced.

If you are using a very old chemical that has potentially already expired, you run a great risk of having a contaminated hot tub and risking your health.

How Long do Hot Tub Chemicals Last?

Most pool chemicals have a shelf life of 3 to 5 years when stored properly:

Things that might extend the lasting effects of the chemicals are:

1. Cool, constant temperatures, in a dry, dark place.
2. Tight-fitting pail and bottle caps and sealed inner bags to exclude moisture and contamination.
3. Chlorine granules may dissolve packaging, repackage for long-term storage.
4. Keep all pool chemicals out of reach of children.

Do Hot Tub Test Strips Expire?

Do not use expired test strips. Most test strip containers have an expiration date somewhere on the container.  Always look for this date when using or buying test strips. Regardless of how the test strip container is stored or handled, test strips have a specific shelf life and should not be used once the product has expired. Using test strips after this date may produce inaccurate results. Therefore, replace all expired bottles.

Do Chlorine Test Kits Go Bad?

Yes. The reagents should not be trusted for more than 12 months.

Also, where you store the test kit affects the shelf life of reagents. Storing your chlorine test kit in a cool and dry place is better (longer lived) than in a hot and moist place.

And as long as you’re getting a new kit, might I recommend a Taylor K-2006. They are great kits and come with a mini chemical handbook that has excellent information concerning your hot tub water chemistry and how to do it.

There are many reagents that are readily available for the Taylor line of test kits.

How Long does a Chlorine Puck Last?

Chlorine puck life actually has nothing to do with the size of your hot tub.  

What affects the life of a three-inch chlorine puck?

Three things:

1) The way the chlorine tablets are placed in the hot tub. For example, whether they are placed in a feeder, floater or skimmer.

2) Hot tub temperature – chlorine pucks tend to last longer in cooler temperatures.

3) Pump or power supply settings

1. Skimmer: The life of your chlorine tablets will depend on how long the pump runs throughout the day when your tablets are placed in the skimmer.

2. Doser: If you have your chlorine tablets in a doser, the setting of the doser control valve will affect the life of the tablets.

Therefore, the time it takes to dissolve a chlorine tablet varies greatly from one hot tub to another. Stabilized chlorine tablets (also called trichlorine tablets) typically have a shelf life of 2 to 3 days. Slow-dissolving Cal Hypo tablets last 4 to 5 days. 

Remember, it is the physical dissolution of the tablets that determines the shelf life of the water, not the available free chlorine in the water that you test with your test strips and test kits. Free available chlorine levels change with hot tub use, sunlight, CYA levels and the number of 3-inch chlorine tablets used. 

Does Chlorine Go Out of Date?

According to the Scripps Research Institute, chlorine can last about 6 months. After that, it is proven that the chlorine begins to degrade. Even if it is kept in its original bottle, the chlorine becomes 20 percent less effective as the year passes.

When it comes to chlorine tablets, chlorine is lost by tablets over time but if they are still sealed the loss will be minimal and they will still work.

It is important to know how to properly store your chlorine (bottle or tablets). According to Clorox, it should be stored between 50 F and 70 F and protected from direct sunlight when it comes to bottles that are sealed and open.

Although the half-life of chlorine is highly dependent on its quality (since any metals in the water will break down the chlorine much faster), the table at the bottom of this page shows the half-life of chlorine at various concentrations and temperatures. 

How Long does Liquid Chlorine Last?

Roughly speaking, 12.5% chlorinating liquid has a half-life (becomes 6.25%) of about 75 days at 90F, 106 days at 85F, 156 days at 80F, and 231 days at 75F. So you can see that it is very dependent on temperature (which ranges over both day and night).

6% bleach lasts about 3-4 times longer with a half-life (reaches 3%) of about 294 days at 90F, 420 days at 85F, 617 days at 80F and 914 days at 75F.

So if you store your bleach at room temperature, it can last many months, if not years, although some degradation will occur. I know we have some very old Clorox Regular bleach in our laundry room that is still very effective. Chlorine bleach stored outdoors, especially when heated by the sun, degrades much faster. You usually want to use it up within a month or two, and you certainly can’t store it for a whole season unless you’ve kept it artificially cool.

Does Bromine Expire?

Bromine should not go bad particularly if it is properly stored and sealed in a container. It would need another chemical (another molecular substance) to react with in order to lose its power. Chemically it should not react with normal air unless O3 (Ozone) is in heavy concentration.

Bromine will last for at least 2 years if stored in a cool and dry location.

How Long does Bromine Last in Hot Tub?

I find that my bromine consumption rate is pretty consistent which is 3 tablets per week. If you need increased bromine levels, you should shock your hot tub  to regenerate the bromine from the sodium bromide bank. 

Shelf Life of Pool Chemicals