The process of raising free chlorine levels in a pool is called shocking the pool. Shocking should be done once a week during the summer, with adjustments for weather conditions, number of bathers and amount of use.
Test the free chlorine level of the pool
Test the free chlorine level of your pool by using an FAS-DPD test kit.
Add chlorine if needed
The free chlorine level of pool water should be 10 times the combined chlorine level. This point is called break point chlorination. Add chlorine to the pool to reach the break point chlorination level. When the chlorine level reaches its break point, it is able to eliminate contaminates from the pool.
Retest, and add more chlorine if needed
Allow the chlorine to filter through the pool overnight, and retest. The process may be halted when the combined chlorine level of the pool drops under 0.5 or the free chlorine test shows 1.0 ppm or less. Another indication that the free chlorine levels are correct is a disappearance of visible algae, which will give the water a crystal clear appearance. Continue to test free chlorine throughout the summer to maintain the health of the pool and the swimmers.