Can Pool Chemicals Be Used For Hot Tubs?

This article is a guest contribution from Poolonomics, a pool care blog that helps pool owners spend more time enjoying their pool, and less time managing it.

Ever wondered if pool chemicals can be used in hot tubs? After all, hot tubs are essentially just miniature swimming pools with a few extra components, so why wouldn’t they work all the same?

Well, not so fast…

Why Pool Chemicals Aren’t Always Ideal for Hot Tubs

It turns out, that there are a lot more differences between swimming pools and hot tubs than first meets the eye.

Here are a just few to keep in mind:

  • Size. Hot tubs are much smaller than pools which means they not only require fewer chemicals, but the potency of the chemical being used must also be lower to avoid causing structural and bodily harm.
  • Temperature. While pools can often be heated, hot tubs reach a far higher temperature during use which can lead to some very unfavorable chemical reactions when using certain chemicals.
  • Evaporation. The higher water temperature of hot tubs leads to a much faster rate of evaporation, and this process leaves behind a higher concentration of chemicals in the water.
  • Circulation. Hot tub jets are much more effective at circulating water compared to swimming pool jets, meaning the chemicals are more quickly and more thoroughly distributed.
  • Bather load. Hot tubs facilitate more people relative to their size, which means a far higher level of contamination. This comes from bather waste, including sweat, saliva, hair, and various beauty products.

What Pool Chemicals Shouldn’t Be Used in Hot Tubs?

With those key differences established, let’s go over some of the specific pool chemicals you should be careful with when it comes to hot tubs.

Don’t Use Chlorine Tablets

Many pools rely on trichlor chlorine tablets placed in floating dispensers to release a steady stream of sanitizer into the water.

These tablets are very acidic with a pH level of around 3. While pools are able to dilute much of this acid to reduce its lowering effects, the speed at which chlorine tablets dissolve quickly overwhelms the small volume of water in a hot tub.

Overall, despite its popularity among pool owners, trichlor-based chlorine is simply not a good solution when it comes to sanitizing your hot tub.

Go Easy on the Liquid Chlorine

Using liquid chlorine or bleach is another popular method of keeping a swimming pool sanitized, especially because it only has a temporary impact on the pH level of the water.

It does, however, introduce a large amount of salt into the water, which can become considerable over a prolonged period of use.

While all pools and hot tubs contain some level of sodium, hot tubs can quickly exceed a healthy level of salt content, which can eventually lead to corrosion and other issues with your water chemistry.

Go Easy on the Soda Ash

Soda ash (also known as sodium carbonate) is often used in swimming pools to raise both the pH and total alkalinity of the water.

This is used in relatively small amounts for swimming pools, but due to the various differences mentioned above, it’s easy to overdo it with this stuff in a hot tub, leading to a huge spike in your tub’s pH level.

So while it is possible to use soda ash in a hot tub, it’s typically not recommended due to how sensitive they are to this particular substance.

What Pool Chemicals Can Be Used in a Hot Tub?

Now, there are a handful of chemicals that can be used in both hot tubs and pools, even if it’s not necessarily the best option for both use-cases.

You Can Use Bromine

Where most pool owners opt for chlorine as their primary sanitizer, bromine is often seen as an alternative in the event of chlorine sensitivity.

This isn’t the case for hot tubs, with bromine being equally as popular (if not more so) as chlorine when it comes to hot tub sanitation. This is mostly due to the fact that bromine is more stable in warmer water, and doesn’t get used up as quickly.

Note: Whatever you choose to go with for your hot tub, just be sure not to mix the two. This can lead to a very dangerous chemical reaction.

You Can Use Salt

Just like with pools, hot tubs can run on a saltwater system.

These systems rely on a saltwater chlorine generator to actively convert salt in your water into sanitizer, meaning you need to keep your salinity level high enough to ensure the generator has enough salt to work with.

Fortunately, there’s nothing particularly special about the salt you use in swimming pools or hot tubs, so you can use the same stuff in your soaker. Just be sure to use a smaller amount.

Always Play It Safe

If you’re ever unsure about whether a pool product (or any other chemical for that matter) can be used in your hot tub, simply check the label.

Any pool product that can reasonably double up as a hot tub solution will almost always mention this fact on the label. With that in mind, if it doesn’t say it works for hot tubs, just take their word for it.

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