Why did I lose my chlorine?

[coog61]

Two weeks ago my CYA tested at 20. I added stabilizer and waited two weeks to re-test. All other tests over that period were typical with CL = 4-5 and ph = 7.4 to 7.6. Then over 2 days (8 days after adding stabilizer) I lost all the chlorine! Ok, I know I need to SLAM, but what would cause the CL to disappear? SWG lights indicate it's operating. The new CYA is 50. ale:

 

[S1ngram]

From what I understand, you can have algae starting even if your numbers look normal. Have you tested CC? What did that show you?

 

[tim5055]

Why do you need to SLAM? Visible algae, cloudy water?

Just because FC goes to zero you don;t have to do a SLAM unless there is an issue.