Chlorine is a pool and spa owner’s best friend. It’s essential for keeping your water clear, clean, and safe for swimming. Maintaining the right chlorine levels prevents the growth of nasty bacteria and algae that can make you sick.
But it’s not as simple as just dumping chlorine into the water. There’s free chlorine, combined chlorine, and total chlorine, and they’re not all the same. Each plays a different role in keeping your water healthy.
This article will break down the difference between free chlorine vs total chlorine, and it provides a complete guide to maintaining the right levels in your pool or spa.
Understanding Free Chlorine, Combined Chlorine, and Total Chlorine
To understand the difference between free and total chlorine, it’s helpful to understand combined chlorine as well.
What is Free Chlorine?
Free chlorine is the chlorine that’s actively sanitizing the water, killing pathogens, algae, and other unwelcome substances. It exists in the water as hypochlorous acid (HOCl) and hypochlorite ions (OCl-).
Maintaining the right level of free chlorine is key to keeping the water safe and clean. It’s the free chlorine that’s doing the work of eliminating harmful stuff.
What is Combined Chlorine?
Combined chlorine is what you get when free chlorine does its job and reacts with contaminants like sweat, urine, and other organic matter. These compounds are also called chloramines.
Combined chlorine isn’t as effective at sanitizing as free chlorine. It’s also what causes that strong “chlorine” smell and can irritate your eyes and skin. High levels of combined chlorine mean the water is contaminated and needs to be shocked with more chlorine.
What is Total Chlorine?
Total chlorine is simply the total amount of chlorine in the water, both the free chlorine and the combined chlorine. You can calculate it with this simple formula:
Total Chlorine = Free Chlorine + Combined Chlorine
Knowing the total chlorine level isn’t enough. You need to know the levels of both free and combined chlorine to really understand what’s going on in the water.
Maintaining Optimal Chlorine Levels
Keeping your pool water properly balanced is key for safe and enjoyable swimming. Here’s what you need to know about maintaining the right chlorine levels.
Ideal Free Chlorine Levels
The sweet spot for free chlorine is between 1 ppm and 4 ppm. Some sources say 1 to 3 ppm is fine, with 3 ppm being optimal, while others advise staying between 2 and 4 ppm.
The important thing is to make sure your free chlorine level is higher than your combined chlorine level.
Addressing High Combined Chlorine
If your combined chlorine is too high (above 0.4 ppm), it’s a sign that something’s not right. You might notice a strong chlorine smell, and the water won’t be as effective at killing bacteria.
The solution is to “shock” the pool. This involves adding a large dose of chlorine to raise the free chlorine levels and break down the combined chlorine.
Consequences of Imbalance
If your free chlorine dips below 1 ppm, you’re increasing the risk of contamination. On the other hand, if your chlorine levels climb above 6 ppm, you might experience eye and skin irritation.
Testing Your Pool Water
To keep your pool water clean and safe, you’ll need to test it regularly and adjust the chemicals as needed.
How often should I test my pool water?
Plan to test your pool water at least two or three times a week.
What are the best testing methods?
Here are a few common ways to test your pool water:
- Pool water test kit. These kits measure pH, chlorine acid demand, and total alkalinity. Dip the test vials about 18 inches below the water’s surface and then follow the instructions that came with your kit.
- Test strips. Just dip the strips into the water, pull them out quickly, and let them dry. Then, compare the colors on the strip with the chart on the packaging.
- Digital chlorine sensor. Reset the sensor before you use it, and then immerse it about 18 inches below the surface of the water. Read the results according to the instructions that came with the sensor.
Frequently Asked Questions
Will shock raise free chlorine?
Yes, shocking your pool is a common way to raise the free chlorine (FC) level. Pool shock is essentially a concentrated form of chlorine, so adding it to your pool delivers a significant dose of FC, helping to sanitize the water and eliminate contaminants. Always follow the product instructions for proper dosage.
Which is more important, total chlorine or free chlorine?
Free chlorine (FC) is the more important measurement. While total chlorine (TC) tells you the total amount of chlorine in the water, FC indicates the amount available to sanitize. High TC with low FC suggests that much of the chlorine is bound to contaminants and not actively disinfecting.
How do I raise the free chlorine in my pool?
The most common way to raise FC is by adding chlorine, either in liquid, granular, or tablet form. You can also use pool shock, especially if you need to rapidly increase the FC level. Make sure to test your water chemistry regularly and adjust the chlorine level as needed.
How much free chlorine should be in a pool?
The ideal free chlorine (FC) level in a pool is typically between 1 and 3 parts per million (ppm). Maintaining this range ensures effective sanitation without causing irritation to swimmers. Test your pool water regularly and adjust chlorine levels as needed to stay within the recommended range.
In Closing
Knowing the difference between free and total chlorine is more than just pool trivia. Keeping your free chlorine levels in the right range is critical for making sure your pool water is safe and clean.
To recap, test your water regularly, and adjust the pH and other chemicals to keep your pool properly balanced. Shocking your pool from time to time will keep the chlorine working effectively.
By following the tips provided here, you can create a healthy pool environment for yourself and your family.