Balance

• While chlorine is important to keep the water clean, the other factors that affect chlorine are the right pH, alkaline, calcium and acid levels. Ideally, the pH needs to be between 7.2 and 7.8. The total alkalinity should be 80 to 100 ppm, the calcium hardness from 200 to 400 ppm and cyanuric acid between 30 and 50 ppm. Perform weekly testing to ensure these levels are correct and constant. Balanced water keeps chlorine working longer and better.
  
  

Test

• If the water in your pool is balanced and you are still having problems keeping the chlorine levels stable, you may have some organisms eating it before it can build up. Take a sample of your pool's water to a pool supply store to have an analysis done. Residual cyanuric acid can turn to ammonia and will require a huge dose of chlorine to remove.
  
  

Shock

• A shock treatment involves adding a large dose of chlorine to the pool at one time in order to raise the chlorine level. If your pool has a strong chlorine odor, you need to shock it to get rid of the organic matter that has bonded to the chlorine, turning it into combined chlorine. Any chlorine added, after these contaminants are removed, will build up the free chlorine level in your pool.