How Often Should You Put Chlorine in a Hot Tub?

Portrait of young woman sitting in swimming pool

Chlorine is used in hot tubs all the time, and some people know it breaks down quickly in hot water. So, how often should you put chlorine in a hot tub?

Here’s what I know, having owned 4 hot tubs:

Plan to add chlorine sanitizer to a hot tub every 2-3 days and chlorine-based shock approximately every 7 days. But the size of the hot tub, the frequency with which it is used, and the number of people soaking will have an impact on the need for chlorine.

But start small.

You can always add more. However, if you overdo the amount or the frequency, you may have to wait for the chlorine amounts to drop to a safe level.

The above is just the tip of the iceberg. In the article, we’ll explore other related issues around chlorine use, shock, the best shock, whether bromine is used less often…

Let’s dive right in…

How long does chlorine last in a hot tub?

Chlorine sanitizer added to a hot tub will last approximately 3 days. The heat of the water will naturally reduce chlorine levels even if no one uses the hot tub.

The fact that chlorine breaks down so quickly is why many hot tub owners use bromine instead.

How long chlorine lasts in your tub also depends on the presence or absence of biofilm. Biofilm? Yeah. It’s a group of microorganisms such as protists, fungi, and bacteria.

Biofilm is usually residing (collectively, of course) deep in the plumbing of your hot tub.

They’re resistant to sanitizers.

So, you could find it highly frustrating that you have to use a lot of chlorine, and yet, there’s little to show for it.

And, it’s easily dissolved in the warm atmosphere of hot tub water because it yields easily when affected by heat.

This is why you may have to use it daily.

Curious to find out the key differences between chlorine and bromine?

Check out a recent article of mine. A lot of people prefer bromine (yours truly included) because it’s stronger in the face of heat and so it’s longer-lasting. And, you can get into the hot tub faster after applying bromine.

Just click the link to read it on my site.

What happens if you put too much chlorine in a hot tub?

When too much chlorine is added to a hot tub, the acrylic shell, the underside of the cover, and the headrest pillows can be damaged or bleached. Soaking in high chlorine can also lead to nausea, vomiting, or skin and eye irritation.

Chlorine is the same chemical in bleach, and like all chemicals, it has to be applied in the right quantity and frequency.

One should never use a tub where the chlorine level is above normal.

The hot tub’s acrylic surface, cover, filter, pillows… can be easily damaged if the chlorine level is too high. Its internal systems may also degrade in time.

Note that these are not covered by the manufacturer’s warranty. And, it shouldn’t, if you think about it.

The water’s acidity is also increased because excessive chlorine lowers the water’s pH. But, perhaps the scariest effect is on the health of bathers.

A sudden feeling of nausea and vomit, dull pain in the chest, and a burning sensation in the throat, skin and eye irritation, asthma, lung irritation is a few of the potential hazards of soaking in over-chlorinated water.

And you can’t detect if you’ve applied too much by smelling the water.

That “chlorine smell” is deceptive: it’s not an indication that the water is over-chlorinated. Instead, it shows there’s a low level of chlorine. What you’re smelling are chloramines.

Chloramines and bromamines fool your test strips!

You may think there’s adequate chlorine or bromine and ensured that subsequently, you apply the recommended amount. You’ve sanitized the tub using chlorine (or bromine, if that’s your thing), and you’re eager to soak and chill out, but you’re curious to know how long one should wait after applying a sanitizer before using the hot tub.

Luckily, that’s the theme of a recent article of mine. Of course, the answer depends on what sanitizer you use and if you use powder, liquid, or tablet. But there’s 1 way to get in immediately!

Just click the link to read it on my site.

Is hot tub shock the same as chlorine?

Hot tub shock can be chlorine-based or non-chlorine. But chlorine-based shock is a different concentration from chlorine sanitizer. Shock reactivates chlorine sanitizer which becomes inert after removing viruses and bacteria from the water.

Both oxidizers (shock) and sanitizers are indispensable in having a sanitary and safe hot tub, but they are not the same.

Sanitizers are the most critical chemical one needs in having a hot tub in great shape. Shock reactivate sanitizers in addition to killing organic matter and removing non-bacterial contaminants.

Now, after a sanitizer has been applied for a while, chloramines or bromamines are formed. These are waste products.

Both are formed when chlorine combines with ammonia (if chlorine is used), making the chlorine less effective, or when bromine combines with ammonia. Bromines and chlorine exist as tablets and granules (powder). 

When the water is oxidized (shocked), these free chlorines are released from the “bondage” to work more effectively. In effect, chloramines and bromamines are converted back to chlorine and bromines.

You can see that a shock is different from chlorine or bromine.

Shock is a chemical that works by breaking down organic matter. It takes its electrons when it meets particles and ensures that your hot tub water is clean and safe.

I devoted a recent article of mine to explore what oxidizers are. Oxidizers? That’s a technical name for shock. You do remember, right?

Just click the link to read it on my site.

Do you add bromine less often than chlorine in a hot tub?

Bromine is applied less often than chlorine to a hot tub because it is more resistant to heat and is consequently longer-lasting. While chlorine sanitizer might be added every 2-3 days, bromine can be added every 4-5 days.

As such, there is no need to apply it as often as one would apply chlorine. It is also less pungent and gentler on the skin.

Both bromine and chlorine are from the same chemical family. Naturally, both are effective and work in similar ways.

They are slightly different.

Chlorine oxidizes, while bromine ionizes. It converts contaminants to ions and forces them apart.

But, the key difference is that bromine is hardier when exposed to hot water. So, it takes a longer time before it’s fully dissolved.

Chlorine, its cousin, on the other hand, is more vulnerable to heat. It disperses faster. This is why it is applied more often than bromine.

And, even though both are impacted by contaminants, such that chloramines and bromamines form, bromine, even in that “trapped” state retains its sanitizing power more than chlorine.

Another reason you’d need to replace it as often.

What is the best shock for a hot tub?

Spa Essentials Dichlor Chlorine Shock is the best shock for a hot tub. It is a multipurpose shock that removes unpleasant odors and restores water clarity and safety. And it can be used in chlorinated or brominated hot tubs.

CLICK HERE to check it out on Amazon.

Spa Essentials is a chlorine-based shock (sodium dichlor). When you apply it, you’re in effect applying an ample dose of chlorine to the water.

This serves to remove non-organic contaminants and kill off bacteria.

In essence, it complements the work of your sanitizer. And, in addition to this, it makes the sanitizer more effective by releasing it from the jail where chloramines or bromamines have kept it.

Spa Essentials is easy to use, highly affordable, and it’s got almost 450 reviews on Amazon, and almost all are rated 5-star.

CLICK HERE to check it out.

Say you’ve been using bromine, can you use a chlorine shock? Check out a recent article of mine where I explained that you can, but that both must not be used in powdered form.

I also said to note that using a chlorine shock would raise the hot tub water’s chlorine level. So, use a test strip, and wait a while before soaking.

Just click the link to read it on my site.


Chlorine is the most popular hot tub sanitizer.

In this article, we looked at how often it should be used. It’s possible to overuse it. And, it is possible to use too little.

We checked out how long it lasts and what happens when you use too much. There are dangers if a hot tub is over-chlorinated—dangers to the hot tub and the bathers.

We also checked out whether shock and chlorine are the same. No, they are not.

Jeff Campbell

Jeff Campbell is a husband, father, martial artist, budget-master, Disney-addict, musician, hot tub lover, and recovering foodie having spent over 2 decades as a leader for Whole Foods Market.

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