What Is a Chlorine Neutralizer? How to “Neutralize” Chlorine In Your Pool

Written by Michael Dean
November 28, 2023

putting chlorine neutralizer into pool

The list of pool chemicals you need to use in a pool can quickly pile up, making it easy to lose track of what is what. Chlorine is the most common chemical used in swimming pools and is very important for sanitizing your water. That said, there is such a thing as too much of a good thing, and when your pool water is overchlorinated, you’ll need to use a chlorine neutralizer.

In this article, I’ll go over everything you need to know about chlorine neutralizers, including what they are, why you should use them, how to use them, alternatives, and more. Let’s get started!

Main Takeaways

  • Most chlorine neutralizers contain the active ingredient sodium thiosulfate.
  • A chlorine neutralizer works to protect you and your pool equipment from chlorine damage.
  • Alternatives to chlorine include sunlight, hydrogen peroxide, vitamin C, and dilution.

What Is a Chlorine Neutralizer?

As you might be able to guess from its name, a chlorine neutralizer is a chemical used to remove (or neutralize) chlorine from the water. As a pool owner, you should already know the importance of properly maintaining your chemical balance. One of the most important chemicals to maintain (if you have a traditional chlorine pool) is the chlorine levels. You should ideally keep your chlorine levels at between 2 and 4 ppm. Too little chlorine and your swimming pool won’t be clean. But, too much chlorine can lead to a host of unwanted problems; more on this later.

Miscalculations happen. Trust me, I’ve been there! It is very easy to make a blunder when shocking or adding chlorine to your pool and add WAY too much of the chemical. Chlorine neutralizers are a quick and easy way to balance the chlorine level in a pool if you accidentally add too much. While you can typically wait for the sun to do its magic, chlorine neutralizers greatly help eliminate high chlorine levels quickly.

How Do Chlorine Neutralizers Work?

Most chlorine neutralizers used in pools contain the active ingredient sodium thiosulfate. Besides sodium thiosulfate, other chlorine neutralizers include sodium metabisulfite, sodium sulfite, and sodium bisulfite. When the neutralizer is introduced to your pool, the product reacts immediately with the free and combined chlorine compounds present in the water to create inactive compounds. This lowers the amount of chlorine present in the pool. Most chlorine neutralizer products can quickly fix an over-chlorinated pool within just a few minutes, making them an excellent option for pool owners looking for a quick fix!

Why Use a Chlorine Neutralizer?

So, why should you use a chlorine neutralizer in the first place? Well, there are a couple of reasons you should keep in mind!

Swimmer Safety

High chlorine levels can irritate the skin, eyes, and lungs of swimmers. In more severe cases where your chlorine levels are astronomically high, swimmers may experience chlorine poisoning! Swimming in a pool with high chlorine levels can cause redness, itching, and difficulty breathing. A chlorine neutralizer sorts this out, bringing the pool water back to safe chlorine levels and making the pool safe to swim in. While chlorine is necessary for safe swimming, as it keeps contaminants and algae at bay, too much of anything is not always a good thing!

Pool Protection

Besides affecting the health of swimmers, high levels of chlorine in the water can harm pool equipment and surfaces. Your pump, heater, cleaner, and filtering equipment are at risk of staining and corroding. This looks bad and shortens their lifespan, costing you money in the long run. Too much chlorine can also lead to damage on concrete surfaces. A chlorine neutralizer works to protect your pool equipment and surfaces from chlorine damage.

I cover why high chlorine levels are bad in more detail below!

How to Neutralize Chlorine In Your Pool

So, now that you know why you should use a chlorine neutralizer, here’s my step-by-step process on how to use it.

Step One: Test the Water

First, determine how out of whack the chlorine level is in your pool by testing the water. Make sure the test strip or liquid test kit is fresh and not expired. Your chlorine levels should be between 2 and 4 ppm (parts per million). If it’s above 4 ppm, proceed to the next steps!

Step Two: Calculate How Much Chlorine Neutralizer You Need

Depending on the levels of chlorine, calculate the amount of chlorine neutralizer you need to add to your pool according to the manufacturer’s instructions. However, as a general rule, you’ll need to add around 2 ounces of sodium thiosulfate for every 10,000 gallons of water to reduce chlorine levels by 1 ppm. If you’re unsure, err on the side of adding too little rather than too much! In fact, I recommend using around ⅓ of the amount you calculate. 

Why only a third? It gives you room for error. If you add too much, you’ll have to recalculate the other way and add more chlorine to your pool. Adding smaller amounts of neutralizer in several increments allows you to adjust the chlorine level accurately.

Step Three: Add the Chlorine Neutralizer

Once you have calculated the amount, dilute the chlorine neutralizer in a bucket of water. Then, add the mixture to your pool and turn on your pool pump. After pouring the neutralizer into your pool, let your pump run for around an hour to circulate the chemical evenly.

Step Four: Retest the Water

After an hour has passed, test the levels of chlorine present in the pool water again. It should be within the recommended levels, but if your levels are still reading over the 4 ppm mark, wait another hour or so. Repeat the above steps if the chlorine level has still not settled after a couple of hours.

Alternatives to Using a Chlorine Neutralizer

Chlorine neutralizer is one of the quickest and most effective ways to lower your chlorine level, but it certainly is not the only way.


The all-natural way! If you have time and patience and your pool is outdoors, you could simply wait to let the chlorine levels dissipate naturally with the help of sunshine. The UV rays present in sunlight are an effective chlorine neutralizer, breaking down chlorine over time. All you have to do is remove your pool cover and expose the water to direct sunlight for a couple of days, and you’ll find the chlorine levels will significantly reduce. However, with this method, you’ll need to keep a couple of things in mind:

  1. If your chlorine levels are super high, this method may take longer than you’d like.
  2. If the chlorine you use includes cyanuric acid or is stabilized, this method may not be the most effective.

Hydrogen Peroxide

Hydrogen peroxide is another chemical that can help neutralize chlorine. It is often used as a chlorine neutralizer in place of sodium thiosulfate. Use a hydrogen peroxide that is specifically for use in pools. For maximum effectiveness with this method, you should ensure the pool’s pH is at least 7.

Vitamin C

Vitamin C, or ascorbic acid, is another excellent alternative to sodium thiosulfate. In particular, this is a good option if you have extremely high chlorine levels, as ascorbic acid works fast and is non-hazardous. However, vitamin C is a slightly pricier alternative than other chlorine neutralizers. It also tends to decrease the pool’s pH, so make sure to test your pH levels after using it.


Another way to reduce your pool chlorine levels is to dilute the water. Adding fresh water to the pool dilutes the chlorine levels present in the water, although it can be a bit time-consuming. Do not drain the pool entirely – simply partially drain and refill it. You may need to rebalance all chemicals after adding the fresh tap water. As a partial drain and refill can be a bit of a pain and, not to mention expensive, I personally recommend using a chlorine neutralizer or one of the above methods instead.

Are High Chlorine Levels Bad?

Yes, high chlorine levels in a pool are absolutely bad. While chlorine is an essential pool chemical for killing off bacteria and other microorganisms, it can do more harm than good in high doses. In high enough concentrations, chlorine can be pretty harmful to our health, not to mention bad for your swimming pool.

Here’s a quick look at what chlorine can do to your body:

  • Skin and hair damage: High levels of chlorine will dry out and irritate the skin, especially people with sensitive skin. It can exacerbate any underlying skin problems, too, such as eczema or a rash. It can also damage your hair, making it frizzy, dry, and brittle. In the case of dyed hair, chlorine can even turn your hair green!
  • Eye irritation: High levels of chlorine can also irritate and damage your eyes—it can lead to redness, burning, and itching in the eyes. If this happens, immediately exit the pool and rinse your eyes with clean, fresh water.
  • Respiratory problems: If the levels of chlorine in the pool are high enough, you could encounter difficulty in breathing, asthma, bronchitis, irritation in the lungs and throat, and other sorts of respiratory distress.
  • Chlorine poisoning: In high enough concentrations, chlorine can be poisonous—in some situations, it can even be fatal! If you experience any symptoms of chlorine poisoning, such as extreme nausea, vomiting, dizziness, and any difficulty breathing, visit the emergency room ASAP!

Can You Swim with High Chlorine Levels?

No. I do not recommend dipping into a pool that you know has high chlorine levels. Considering what I’ve covered so far on what high levels of chlorine can do to your body, it goes without saying that exposing yourself to large amounts of the chemical is not a good idea. Always test the water before swimming! If the chlorine levels are above 4 ppm, it’s too high and needs lowering before you and your family can safely enjoy the pool.

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Frequently Asked Questions

Does vinegar neutralize chlorine in water?

No, vinegar does not neutralize chlorine in water. However, vinegar can come in handy to counteract some of the effects of too much chlorine, including green hair!

What is the fastest way to lower free chlorine?

The quickest way to cut down on high chlorine levels is to use a chlorine neutralizer. After adding it, test the water half an hour later to ensure the chlorine is within the correct range, and then feel free to jump back in the water!

Swim Safely with Chlorine

As you can see, chlorine neutralizers are super handy for anyone looking to lower their high chlorine levels. Since they work quickly, they’re an excellent solution when time is of the essence. However, a word of caution: Adding too much chemical neutralizer can result in persistently low chlorine levels over several days. So, always start with a lower dosage and make gradual adjustments to ensure you don’t harm your pool’s ability to kill off bacteria and germs.

Any questions? Leave me a message! I’ll be happy to help out. Head to my main research article on swimming pool maintenance tasks for more related advice.

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