Available Chlorine

Also Known As: Free Chlorine

Available chlorine content (ACC) compares the potential oxidizing power of chlorine compounds. In it’s purest form, chlorine is a highly toxic gas, which is difficult to handle. Therefore, additives are mixed with chlorine to create liquid, tablet, shock and granular forms.These additives dilute the chlorine, allowing it to change form for storage and safe handling. The available chlorine is represented as a percent, indicating the amount of pure chlorine in the mixture.

Chlorine gas contains 100 percent available chlorine and is the basis of determining the chlorine content in other compounds. The most concentrated of these compounds are chlorine tablets, with 90 percent available chlorine. Shock chlorine varies from 65 to 75 percent available chlorine. Granular has 55 percent available chlorine, and liquid chlorine has only 15 percent or less.

In addition, available chlorine can be measured in the pool water. Available chlorine in a pool should be between one and four parts per million to properly disinfect. Maintaining an optimal level of free chlorine is critical for safe water chemistry.

Free available chlorine is the measure of the chlorine’s active disinfecting power. A pool’s pH can affect its free available chlorine. A pH of between 7.2 and 7.8 is ideal, as it keeps chlorine most active.