I am by no means a pool expert. We had a very cloudy pool at the start of the season. We tried shocking it and the chlorine levels were either high or just right and still cloudy. We took a water sample to our local pool place (Leslie's) and found out the CYA was very high. We had to drain 2 feet of water and add fresh, get the levels right and now it's fine. BTW, my pool is in ground so I'm not sure if that makes a difference.