How Much Chlorine Is Needed in a Hot Tub? - Backyard Boss
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How Much Chlorine Is Needed in a Hot Tub?

You may not know it, but you are exposed to chlorine on a daily basis. Used to kill germs, we have become dependent on the powers of chlorine to keep us safe without even truly knowing why. Especially important is its use for water sanitization to keep us from ingesting or being otherwise exposed to illnesses.

If you own a pool or hot tub, then most likely know you need it, but do you know how much you are using and why? The following article explains what it is, why it is important, and how much chlorine is needed in a hot tub.

What Is Chlorine?

Hand holding Chlorine Pellets with inflatable pool on background

Chlorine is a chemical made using ordinary table salt, hydrogen, and sodium hydroxide. It is an efficient disinfectant and is used to help create a more sanitized life for people all around the globe. Used in a wide variety of products, it is most popularly known for keeping your water clean. Everything from drinking water to your pool, and hot tub, depend on chlorine to keep you safe from waterborne pathogens that can make you ill.

When used as directed, chlorine is very safe, but care should be taken to use proper concentrations and to avoid mixing it with other chemicals. When used improperly it can cause skin irritation or even contribute to toxic vapors.

Why is Chlorine Needed for a Hot Tub?

Hot tubs serve as a giant, warm soup of hair products, skin oil, lotions, dirt, and debris if you don’t keep it treated with something that is able to kill off any potential bacteria and free floating germs. So this is one of two effective chemical products (that are interchangeable with one another) that work with your filtration system and cleaning schedule to provide you a safe soaking experience.

Although you may be hesitant to expose yourself to chemicals, you will need to add chlorine (or bromine) to shock the hot tub at the very least. Using certain cleaning alternatives between shocks can help lower levels and reduce chlorine use overall as an alternative to daily treatments without sacrificing safety.

What Kind of Chlorine is Used in a Hot Tub?

tester with tablet and powder of chlorine or bromide for mainteance of water quality of jacuzzi or spa

If you choose to use this option over bromine, then you actually have a few choices to pick from. Most popular for tubs are sodium dichlor granules that dissolve quickly and are basically pH neutral so you don’t have to worry about affecting pH levels.

You also can also use plug in salt systems that produces pure chlorine from mineral salts. These systems do not require any modifications to your existing system and are good for consistent sanitation.

Trichlor pool tablets and calcium hypochlorite are excellent for pools, but may not be a great choice for hot tubs due to the high acidity and slow dissolve rate- making it less effective. Contact with your tub shell can even bleach it of color. Unless you have a large spa, you may want to stick with other options.

How Often is Chlorine Added to a Hot Tub?

When you add the chemical to water it is called free chlorine. Once it interacts with oils, bacteria, and other yuckies, it is called combined chlorine- and you will shock your water with a higher concentrate to get rid of it. This generally should be done, at a minimum, once a week, or more if the tub is heavily used.

You can also add it between shocks in lower levels to help keep water at healthy, maintained levels.

How Much Chlorine is Used in a Hot Tub?

Jacuzzi spa pool qualiter water tester and tablet of chlorine or bromide

Chlorine levels are measured in parts per million (ppm). A spa should have between 1.5 and 3 ppm (up to 5ppm is safe) at all times to ensure a clean water environment for soaking. You can test water easily with kits found at your pool stores, and online and add as needed.

If you are wondering what to add per gallon, manufacturers make it easy for you using easy measurement guides. It is important to follow these guidelines because each brand may be slightly different. In general, 2 teaspoons of chlorine per 200 gallons diluted in water and poured into a circulating tub will generally help raise chlorine levels quite quickly without overdoing it. You should test your chlorine levels every few days and adjust as needed.

Shocking the tub is designed to raise the levels to between 8 and 10 ppm to help remove any combined chlorines and get rid of anything lingering that hasn’t already been broken down through the system.

How Long to Wait After Adding Chlorine Before Use?

Hot tubs in spa center

There is no hard and fast rule applied to this, but you definitely want your ppm levels at or below 5 before getting in for a soak. High levels can cause skin irritations, bleach materials, or even eat away at synthetic fibers. Allow the chlorine to do its job to dissolve foreign wastes before introducing more to the system. Some people claim the water is fine within 20 minutes after a daily treatment, but you may want to wait up to 24 hours after shocking.


Although there is no fast and easy universal measurement of adding chlorine to your hot tub, you should be well aware of the differences in applications and why it is used. Always make sure to measure properly according to the package no matter whether you are using granules, liquid, or tabs.

Keeping your chlorine levels where they belong is essential to a clean, bacteria free water. Be sure to adhere to a strict schedule to ensure you are never exposed to contaminants. But remember, chlorine doesn’t work on its own- and you will have other substances you need to be aware of for clean water purposes.

We’d love to hear below which chlorine products for hot tubs are your favorite. And, as always, please share.