Why Does The Chlorine In My Hot Tub Disappear?

When you add chlorine to the hot tub, it gets used up after some time. Usually, you add chlorine to high levels of 8 – 10 ppm. The chlorine disappears while sanitizing your hot tub, and the levels usually drop to 2 – 4 ppm.

So, why is the chlorine in my hot tub eaten up quickly?

Your chlorine disappears from your hot tub because:

  • Your water is highly contaminated
  • Your pH and total alkalinity levels are out of balance
  • You use your hot tub too often.
  • Your hot tub is directly exposed to the sunlight

Do you Put Chlorine in Hot Tubs?

Yes, chlorine serves as a sanitizer in a hot tub. Otherwise, you could end up with a mold, algae, and bacteria infestation in the spa. As an alternative, you can use bromine as a sanitizer. Bromine is, however, more expensive than chlorine. If you’re operating on a tight budget, then chlorine serves the purpose of making sure your water is safe for use.

Contaminated Water

If the water is highly contaminated, the chlorine has to work extra hard to sanitize it, thus making it deplete really fast. Water gets contaminated if you get inside without taking a shower first. Also, debris blowing in if you leave the spa uncovered or spilled drinks can contaminate the water.

Wrong pH Levels

If the pH levels and total alkalinity of the water are imbalanced, your chlorine gets used up very fast as it tries to balance the water chemistry. To avoid such a problem, you need to check the pH levels of the water as a regular routine.

Frequency of Using the Hot Tub

How often and how long do you use the spa? Lately, have you been spending more time in the hot tub? It could be the reason why the chlorine gets depleted fast. The more you use the hot tub, the more the chlorine needs to work to sanitize the water after you.


Chlorine also gets depleted fast if exposed to direct sunlight. If the weather changes to more sunny days, your chlorine levels could go down faster. It would help to put up an umbrella above the spa and also cover it while not in use.

What Happens if you Get in a Hot Tub with Too Much Chlorine?

Too much chlorine in a hot tub can irritate your skin, eyes, and lungs. Chlorine, as a bleaching agent, can also bleach your hair. Safe chlorine levels should range between 2 – 4 ppm while anything above that is unhealthy.

How Long does it Take for Chlorine Levels to Drop in a Hot Tub?

It can take a few hours or even a whole day for the chlorine levels to go down. You need to test the chlorine levels to determine whether the levels are between 2 – 4 ppm before you can use such a hot tub.

Why do I Have to Put Chlorine in my Hot Tub Every Day?

When you add chlorine to your hot tub water, it becomes hypochlorous acid. The acid is what reacts with bacteria and other contaminants making your water safe. In fighting bacteria and other elements, the chlorine molecules become inactive, which is why you need to put chlorine in the spa more often.

How do you Raise the Free Chlorine Level in a Hot Tub?

Before learning how to raise free chlorine levels, let’s understand some basic terms. When testing for chlorine levels using a test strip, you know the levels of free chlorine, combined chlorine, and total chlorine.

Free chlorine is one that isn’t combined with any molecules and is available for sanitization purposes. Combined chlorine has already been combined with contaminants and other molecules during the sanitization process. Total chlorine is the amount of free chlorine plus combined chlorine in the spa.

If the total chlorine reading is high, but the free chlorine levels are low, your spa needs a shock treatment. To do this, you need to use an oxidizer that destroys waste and chloramines, raising the free chlorine levels in the hot tub.

What Are the Side Effects of too Much Chlorine?

Despite being a practical and budget-friendly sanitizer, chlorine has several side effects listed here.

  • Irritates the skin and eyes if used in high concentration
  • The fumes emitted can cause respiratory illnesses
  • Bleaches the hair and the spa shell over time
  • Exposes hot tub users to risks of skin cancer

How Long does it Take for Chlorine Levels to Go Down?

Depending on whether you’re administering a chlorine shock or simply sanitizing your water, the chlorine levels could go down after about 24 hours. Make sure to test before using the spa. The recommended chlorine levels are between 2 – 4 parts per million.

How Often Should I Put Chlorine in my Hot Tub?

The frequency at which you add chlorine to your hot tub depends on your usage. The more you use the hot tub, the faster chlorine gets depleted. You need to add chlorine each day if you use your hot tub more often. Otherwise, every 2 – 3 days can help maintain clean and safe water.

How Soon can I Use the Hot Tub After Adding Chlorine?

It’s not safe to jump into the spa immediately after adding chlorine to it. You want to make sure that all the chlorine has dissipated before using the water. It takes between 30 minutes to one hour for the chlorine to dissolve.

Is it Safe to Go in a Hot Tub with Low Chlorine?

No, it’s not safe to use a hot tub with low chlorine levels. Low chlorine implies the ineffective sanitization of the water. The warm temperatures in a hot tub combined with low chlorine levels make a good breeding ground for bacteria.

What do I do if my Chlorine is too High?

It’s possible to put in more chlorine than you actually need in the hot tub. Luckily for you, it’s possible to restore the right quantity in simple steps.

Stop Using the Spa

If the levels are higher than the recommended, stop using your hot tub for a day or two. To speed up the process of lowering chlorine levels, remove the cover to expose the water to direct sunlight.

Use a Neutralizer

Sodium thiosulfate acts as a chlorine neutralizer if you really need to use the spa sooner. Add the neutralizer gradually, making sure to read the test readings only to use the right amount.

Drain the Water

The last option is draining the water with too much chlorine and refilling with fresh water. Once the tub is filled with water, now add the correct amount of chlorine.

How do you Neutralize Chlorine?

Here are some of the ways you can neutralize chlorine in your hot tub.

Use a Neutralizer

Neutralizers like sodium thiosulfate help to lower the chlorine levels in your hot tub. Make sure to add the neutralizer gradually until you achieve your desired chlorine levels.

Hydrogen Peroxide

Hydrogen peroxide works by converting chlorine to oxygen and water, thus lowering chlorine levels in the spa.

Diluting the chlorine

Drain half the amount of water in the hot tub and add fresh water to fill the spa. By doing so, you neutralize chlorine levels in the hot tub.

What Chlorine Should I Use in my Spa?

Only use granular chlorine meant for hot tubs in your spa. Avoid liquid chlorine despite being cheaper because it could cause more damages to your hot tub in the long run.

Is There a Difference Between Spa Chlorine and Pool Chlorine?

Yes, spa chlorine and pool chlorine are two different products. A spa uses granular chlorine while a pool uses liquid chlorine. Liquid chlorine doesn’t work well with the high temperatures found in a hot tub. Besides, chlorine meant for pools is highly concentrated and can throw the pH of a hot tub off balance due to low water volumes.

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Emily Williams

Emily is a passionate Hot Tubs researcher who loves writing about all things Hot Tubs! She has years of experience and a knack for simplifying complex concepts, these articles are here to answer all your burning questions in a simple and easy to read style.
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