Strange chlorine

[whitemok]

The pool already had a high chlorine reading of 10.
I turned off the feeder to drop the chlorine.
Next day someone turned off the moter so the pool became green.
Next day I shocked it . I also drained half of 40000 gallons and refill it. At this point I still left the feeder off until the next day when the pool filled up. Even though they were no tabs in the feeder. I still had a reading of 10.
What gives.?

 

[jblizzle]

Please post a full day of test results. Specifically, what is your CYA? If that is very high, a FC level of 10 may not be high enough to prevent algae.

 

[YippeeSkippy]

And does your test kit measure over 10ppm? Which kit are you using??