Why is my Free Chlorine Level So High?

Modified on Thu, 18 May 2023 at 10:54 AM

Typically a high Free Chlorine level means that your Cyanuric Acid level is too high.  For your Free Chlorine (FC) to be effective if you are using Cyanuric Acid (CYA) as a stablizer, you will need to have your FC at 7.5% of your CYA level.   If you CYA level is at 100 PPM, then you will need to have a FC level of 7.5ppm in order to have effective sanitization.

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When the cyanuric acid (also known as stabilizer or conditioner) levels in a swimming pool get high, it can impact the effectiveness of chlorine in sanitizing the water. Cyanuric acid is commonly used in outdoor pools to protect chlorine from degradation caused by sunlight.

Here's how it works: Cyanuric acid forms a protective shield around chlorine molecules, which helps prevent them from dissipating due to ultraviolet (UV) radiation from the sun. This stabilizing effect is beneficial to maintain chlorine levels in outdoor pools.

However, if the cyanuric acid concentration becomes too high, it can start to hinder the chlorine's sanitizing abilities. The excessive presence of cyanuric acid can make it more difficult for chlorine to effectively kill bacteria, viruses, and other harmful microorganisms in the water. This condition is often referred to as "chlorine lock" or "chlorine-stabilizer imbalance."

To address this issue and ensure proper pool sanitation, it is necessary to increase the chlorine levels. The increased chlorine compensates for the reduced effectiveness caused by the high cyanuric acid concentration, allowing it to maintain proper disinfection levels in the water.

It's important to note that maintaining proper cyanuric acid levels is crucial for the overall balance of the pool water. The recommended cyanuric acid concentration may vary based on factors such as climate, pool usage, and the type of chlorine being used. Regular testing of pool water parameters, including cyanuric acid and chlorine levels, is essential to achieve and maintain a safe and healthy swimming environment.

Here is a chart that explains the amount of Free Chlorine you would need to maintain proper sanitization depending on your Cyanuric Acid levels: