When you add chlorine to your pool water, the chlorine will react to form hypochlorous acid, which will further react to form hypochlorite. These ionic compounds are what make up the free chlorine.
Free chlorine in your pool is what kills bacteria and other pollutants in the water. When in action, some free chlorine molecules react with other compounds to form unreactive chlorine compounds.
The chlorine in the unreactive compounds is what we call “combined chlorine.” Since chlorine is bonded with other compounds, it becomes ineffective in killing bacteria.
The sum of the free chlorine and combined chlorine gives the total chlorine in the pool.
We are going through these long details to explain why total chlorine can be higher than free chlorine. It is normal for total chlorine to be higher than free chlorine.
If total chlorine and free chlorine are equal, it means that the chlorine has not started reacting. As long as the chlorine is effectively attacking pollutants, the value of the free chlorine will decrease, making the total chlorine slightly higher.
Nevertheless, total chlorine shouldn’t be higher than free chlorine with a high margin. The margin between total chlorine and free chlorine shouldn’t be higher than 0.2 ppm.
If the difference exceeds 0.2 ppm, it means that the combined chlorine in the pool is very high and needs to be reduced.
At this point, the best way to reduce combined chlorine and increase free chlorine is to shock the pool water immediately.
So should free chlorine equal total chlorine?
No, unless the chlorine in your pool is not reacting, the total chlorine should be slightly higher than the free chlorine.
The slight difference shows that the free chlorine is actively disinfecting the pool. As we stated above, the difference between the two values shouldn’t be higher than 0.2 ppm.
The target value for combined chlorine must always be below 0.2 ppm. Anything higher than that means that the pool needs shock treatment.
What does it mean when total chlorine is high?
If total chlorine in your pool is high, it means that the amount of chlorine in your pool is higher than the ideal range of 1-3 ppm.
The chlorine level in your pool needs to be within the range of 1 ppm to 4 ppm. Once it goes beyond 5 ppm, the water will start irritating the skin. That is when the swimmer starts noticing burning eyes and itchy skin.
However, it doesn’t literally mean that the free chlorine is high. The total chlorine could be high while the free chlorine is low. It’s possible when the combined chlorine becomes too much in the pool, or when the stabilizer in the water is too much.
Can I swim in a pool with too much chlorine?
No, it is not safe to swim in your pool if the chlorine level is too high. Entering the pool could be detrimental to your health if the chlorine level in your swimming pool is higher than 5 ppm.
According to the CDC, some of the health implications of chlorine exposure include:
- Burning eyes and nose
- Chest tightness
- Shortness of breath
- Blurred vission
- Dry skin and hair
- Fluid in the lungs if swallowed
To avoid health complications, especially for those who have health challenges like asthma and respiratory tract infections, do your best to stop using the pool until the chlorine level drops to a safe level.
How do I lower my total chlorine?
The first step you need to take to lower the total chlorine in your pool is to stop adding more chlorine to it.
Lowering the amount of chlorine in your pool water is not difficult. It can even be done naturally without adding any chemicals.
Some of the ways you can reduce the amount of total chlorine in your pool include:
Exposure to sunlight: By allowing your pool to be directly exposed to the UV rays of sunlight, the chlorine in it will deplete rapidly.
Even aerating or agitating the pool helps the pool chlorine deplete fast.
Direct heating: You can also make the chlorine react rapidly by heating the pool water. From our high school chemistry, we learned that high temperatures can help to increase the rate of reaction.
We can apply the same technique in our pool to facilitate the reaction of the chlorine molecules. That helps the total chlorine level drop.
Adding sodium thiosulfate: Apart from the natural methods, this is another reliable method you can use to lower the chlorine in your pool. Interestingly, it is very cheap. About 2 ounces can lower the chlorine in 10,000 gallons of water by 1 ppm.
Adding hydrogen peroxide: You can use hydrogen peroxide to break down the chlorine molecules in your pool. For every 10,000 gallons of pool water, you need about 7 oz. of 27% hydrogen peroxide solution to reduce the chlorine by 3 ppm. Note that the chemical can affect the pH of your pool. So, test your pool to determine the pH.
Adding ascorbic acid: The acid is often used to remove stains from the pool. However, you can also use it to lower the level of chlorine in your pool. For every 10,000 gallons of pool water, 10 oz. of ascorbic acid will drop the chlorine by 3 ppm.
Before you start using any of the chemicals, make sure that you read the manufacturer’s instructions carefully. From the instructions, you will be able to know the right dose to use.
How long does it take for chlorine levels to go down?
Depending on the level, it takes about 1-5 days for your pool’s chlorine level to drop to a safe level.
If the total chlorine is more than 10 ppm, then you may have to wait for over 5 days until it drops.
If you are not patient enough, you can try chemical means to make the process a bit faster.
How do I raise the free chlorine in my pool?
If you want to raise the free chlorine in your pool, you can do so by adding more chlorine sanitizer to the pool if your sanitizer has been depleted a lot or the total chlorine is low.
What do you do if combined chlorine is high? If the total chlorine is still high and the free chlorine is low, the best thing to do is to shock the pool. Since the total chlorine is high, it means that you have a lot of combined chlorine in the water.
To break up the combined chlorine, you need to add enough shock that can be able to break up the combined chlorine. The level of chlorine required to break the used chlorine is called the breakpoint.
Before you can know the breakpoint, you need to measure the total chlorine and free chlorine in the pool with a test kit.
Then, with the values, you will be able to calculate the amount of chlorine change your pool needs. To learn how to fix high combined chlorine, click here to read that in detail.
Will chlorine tablets raise free chlorine?
You can use a chlorine tablet to raise and maintain the free chlorine level in your pool when there is a slight change in the amount of chlorine in the pool.
However, don’t use chlorine tablets in your pool to raise free chlorine when there is an urgent need for free chlorine in the pool. Chlorine tablets are slow-releasing, so they can’t give you the instant chlorine supply your pool needs.
The best thing in such situations is chlorine shock. Shock gives you an instant supply of chlorine.
Why can’t I get my pool chlorine levels up?
You may be wondering why your free chlorine is always low. Well, there are different factors that can contribute to low free chlorine in your pool water.
Some of the factors are:
Presence of algae and pollutants: If there is an algae bloom or accumulation of organic compounds in your pool, there will be a high demand for chlorine in the water.
Direct exposure to sunlight: Not covering your pool or exposing it to sunlight can make the pool chlorine deplete faster.
High level of phosphate: Having high levels of phosphate can contribute to the high demand for free choice.
Low chlorine sanitizer: Your chlorine sanitizer helps you maintain the amount of free chlorine in the pool water. If it’s low, the free chlorine molecules will deplete faster.
Is total chlorine the same as combined chlorine?
Total chlorine is not the same thing as free chlorine. Free chlorine is the active (unreacted) chlorine in your pool.
When you add chlorine to your pool, it reacts to form hypochlorous acid, which further converts to hypochlorite. These ionic compounds are the free chlorine in pools.
When they react, they can form other compounds, and the reacted chlorine is what is known as combined chlorine.
The total chlorine in your pool water is the sum of the free chlorine and combined chlorine in the pool.