My pool seems to be using chlorine much quicker than normal for the past 3 or 4 days. I think I might have something growing in the water and may need to shock it. The water appears clear. Here are my test results from a TF-100 test kit:
Temp: 83 degrees
I have been trying to keep the chlorine level about 8.0 due to the high CYA level. I keep a solar cover on the pool during the day.
Last night when I turned the pool off, the chlorine level was 7.5, and this morning, 12 hours later, the level is 4.5. Normally the chlorine level only drops 1.0 from morning to morning. Usage by the family is the same and the weather is the same as it has been the past few weeks. It may have actually been a little cooler the past three days.
Based on this info, would you think something might be growing in the pool and I should shock it. If so, what level should I raise the chlorine to? Based on the Chlorine / CYA Chart, I should raise it to 26. PoolCalculator.com says 19.0.