Quote Originally Posted by my_youngminds View Post
9am reading:
FC: 18.5
CC: 0
pH: 8.0

Did a backwash and ran the Rover pool vac continuously throughout the day.

3pm did another backwash.

6pm reading:
FC: 7.5! (Isn't that quite a drop? Especially since the weather is cloudy and rainy?)
CC: 0 (which kind of had me confused. Doesn't CC mean something is growing?)
pH: 7.4
Added 2 (182 oz. jugs) of 6% bleach, per the pool calculator's calculations to raise FC back up to 15.

8pm
FC: 16.5
CC: .5
pH: 8.2
This is a GREAT illustration of how high FC levels can cause a false high pH reading! There is a chemical reason for this but the chemistry is somewhat complex so I will spare you the details. Just be aware that pH readings are suspect when the FC is above 10 ppm (but still 'usable, if not totally accurate up to about 15 ppm since the error is not that great).