Also Known As: Free Chlorine
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.