Test the pool water with a reliable test kit
Add liquid chlorine or pool shock
Use calcium hypochlorite, sodium hypochlorite, or dichlor as directed
Follow the product label for the correct dosage
Run the pool pump to circulate the water
Brush the pool walls and floor
Retest the water after circulation
Repeat small adjustments until the target free chlorine level is reached
Keep cyanuric acid and pH in the proper range
Remove debris and clean the filter regularly