How to Easily Sanitize Your Hot Tub—and Stay Safe

This one is for the lucky among us. There’s no way around it: owning a hot tub is one of the best decisions you could make to both relax and host some top-notch social hangs. Even just thinking about water throwing off steam can be enough to make our shoulders sink a little lower. Ahhhh… where was I?

Of course, with great power comes great responsibility. Without proper sanitation, that same hot water that makes spas so enjoyable can also host unwanted bacteria, including pathogens that could make you sick. Thankfully, there’s a way to properly clean your hot tub without the help of a pool service expert—the easy and cost-efficient way. I’ll explain what sanitizing chemicals you need, how to choose them, how much to use, and finally, how to add them to your spa to keep it safe—and sparkling clean, too.

How Do Sanitizing Chemicals Ensure Safe Soaking?

Unfortunately, bacteria share your love for hot tubs. If you have a concerningly low amount of disinfectants circulating throughout your water (or, too-low circulation), the germs which have the capability to make you sick could thrive. That’s exactly what we don’t want, right?

Since this is a matter of health, I’m turning to the Center for Disease Control (CDC)—and believe me, they have opinions. When sanitizing your hot tub, the CDC recommends that you use chlorine or bromine. Both of these will wipe out unwanted germs and keep you and yours soaking safely—as long as they’re applied correctly. Don’t worry, I’ll show you how.

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Are Bromine and Chlorine Equally Effective?

The short answer is yes, bromine and chlorine both work. However, there are pros and cons to each that you should consider when deciding which one is right for you. And by the way: you could change your mind down the road, and that’s okay, too.

It’s widely accepted that bromine is the most popular chemical used for hot water, and for good reason: not only is it effective and inexpensive, but it also has a lower pH than chlorine and can therefore keep your water balance more stable. Plus, it kills for a longer amount of time.

If you have an outdoor spa that you frequently leave uncovered, chlorine granules or tablets might be right for you: they’re more resilient to UV rays than bromine. In general, chlorine tends to kill bacteria more quickly than bromine—but also doesn’t work as long and has to be replaced more often.

Whatever you do, don’t use the same liquid version of chlorine that you might use for a pool. The high heat of your spa will dissolve the liquid so quickly that it won’t be spread in a uniform manner—meaning some pockets of water will have extreme concentrations of chemicals, while others will allow bacteria to grow happily and unhindered.


What About What Bromine and Chlorine Leaves Behind?

If you’re asking this question, then good for you: chances are you’re already well versed on how (and why) to shock your pool and hot tub. For the rest of us, here’s the, ahem, breakdown.

After a bromine particle attacks and kills bacteria or another organic material in your pool, it creates what is called a bromamine (or, if you use chlorine, what is called a chloramine). This is an inactive particle that floats along in your water until it can be broken apart.

Think of the last time you heard there was a hot tub where you were passing through—whether this be at a public space, a hotel, or your friend’s house—and you were excited to step in. But with each step you took closer to the hot tub, the stronger the chemical smell.

Let’s pause there. Contrary to what you might assume, that smell isn’t from chemicals at all—it’s from a lack of chemicals. That smell is chloramines and/or bromamine! And not only do they smell bad, but they greatly reduce how well the sanitizing chemicals you add to your hot tub works.

So here’s another argument for bromine over chlorine: generally speaking, a bromamine is less noxious and harmful than a chloramine. In either case, you should be regularly shocking your hot tub to get these particles out of there—but more on that later.

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 sanitize your hot tub

Got It. So How Can I Properly Sanitize?

Now you have your chemical of choice and you’re ready to wave—or annihilate—those germs goodbye. But let’s take a moment here, and make sure we’re doing it right. Since the effectiveness of your sanitization has a direct link to the health of you and yours, you want to be sure that you’re (1) using the proper amount of chemicals, and (2) adding them the correct way to your pool.

How Much Bromine or Chlorine Do I Need?

It’s imperative, according to the CDC, that your free chlorine level be at least 3 parts per million (ppm). If you use bromine, you’ll want to keep it between 3 to 5 ppm, but 5 ppm is ideal. After you use the amount of chlorine or bromine that is recommended by the specific manufacturer (this tends to differ, so be sure to read the instructions), you’ll want to use test strips to make sure that you’re in the right range of free chlorine or free bromine.

The directions will always be based on how many gallons of water your hot tub contains. If you’re not sure of this number, don’t stress! That’s counterintuitive to the reason we have hot tubs, and besides, it’s simple geometry anyone can do. You just have to multiply the length, width, and depth of your hot tub in feet, and then multiply that figure by 7.5 to convert the number to gallons. Prefer formulas? Follow the one below:

[Hot Tub Length in Feet] x [Hot Tub Width in Feet] x [Hot Tub Depth in Feet] x 7.5 = [Volume of Your Hot Tub in Gallons]

How Do I Add Sanitizing Chlorine or Bromine to My Hot Tub? Do I Just Drop One In?

Okay, so it isn’t as easy as tossing some chlorine or bromine into your water and walking away, job done—but it’s still pretty close. How you add sanitizing chemicals to your hot tub depends on whether you’re looking to use granules or tablets.

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how to sanitize your hot tub

How to Add Granules to Your Hot Tub

First, make sure you have your hot tub volume in mind. Again, this will come in handy later. Turn your hot tub on, and read the instructions on your bromine or chlorine container. Measure the amount recommended by your manufacturer, and pour the granules directly into your hot tub. Allow the water to run for about twenty minutes to both dissolve the granules and spread the chlorine and bromine evenly throughout your water. Then, use test strips to make sure your tub is at 3 ppm if you used chlorine, and close to 5 ppm if you used bromine.


How to Add Tablets to Your Hot Tub

For this one, you’ll need a feeder, floater, chlorine/bromine float, chlorine/bromine dispenser, chlorinator, or brominator—they’re all different names for the same nifty thing. If your feeder is adjustable, go ahead and adjust in accordance with the manufacturer’s recommendations—these instructions will be printed on your chemical’s packaging. This’ll control the rate at which your chlorine or bromine releases. Then, you’ll want to take just a few seconds to hold the feeder under the hot tub to release any remaining air. Over the following few days, use test strips to make sure your tub is at 3 ppm if you used chlorine, and close to 5 ppm if you used bromine.


Think You’re Done? Not So Fast. Here’s the Rubdown.

Okay, so you added the sanitizer of your choice. That’s great, but you’re not quite finished. Part of keeping your hot tub clean is also scrubbing down your spa’s shell, jets, and water line to keep away any scum that might build up. Since you’ve already used some chemicals, white vinegar will do the trick—plus it’s inexpensive and hypoallergenic. Use some on the hot tub cover to discourage mildew, too. You’ll want to repeat this process every week or so.

Every few months, it’s essential that you drain your hot tub water and rub it down with cleaning chemicals or some white vinegar—just make sure that when you’re filling it up again you’re keeping an eye on your water level.

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Chloramines and Bromomines? Shock Them Goodbye.

Remember chloramines and their slight less noxious counterpart, bromamines? Those irritants aren’t welcome here, and you’ll be tempted to reach for the most popular pool shock on the market to be rid of them. But hang on: calcium hypochlorite is not for you. This is because it’s unstabilized, meaning that it breaks down in heat like direct sunlight—and loses 95% of its effectiveness in a hot tub.

There are many types of pool shock on the market, and sometimes it can feel overwhelming to choose. So I’ll just tell you now: to shock your hot tub, you’ll want to use a stabilized shock like dichlor shock, which is also inexpensive and widely available. You should do this about once a week. Trust me, your skin and your nose will thank you.

how to sanitize your hot tub

You’ve Done the Work. Now Get Soaking.

Frankly, you deserve this. You’ve taken the time to make sure that your hot tub is properly clean—and wiping out bacteria that could make you sick and irritating chloramines or bromamines along the way. Now you’re left with water both steaming and sparkling. The only thing I’m going to tell you to do now? Step in, and relax.


Read more on whether you should run a pool heater overnight. Want to know how to heat your pool in an efficient way? Read more here.