I had a large bather load yesterday. Before the swim, I brought FC from 8.5 to 9. I added another 25oz afterwards to raise it another 1ppm per pool math. This morning I noticed it was cloudy and smelled funny, don't know if was ammonia or not. FC was at 7.5. I just checked CYA and it was at 50, checked it twice. Last 2 checks were steady at 70, last one 4 days ago. FC now at 6.5. Any thoughts?
CYA Fell 20
- Thread starter Dan P
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Unlikely to have dropped that fast without water dilution and with chlorine in the water (so bacteria couldn't grow). Perhaps your lighting conditions changed? Are you viewing the tube with your back to the sun so that your body is shading it and you look straight down into it?
Holding it at waist level, same location inside the house with no lighting as always. Might add that after adding the chlorine last night the pump turned off as it was scheduled to do so. I will recheck tomorrow morning again before adding any CYA.
So usually indoor lighting is not nearly bright enough so generally your readings indoors will have the test read a CYA that is higher than it actually is. Try standing outside with your back to the sun and you shading the tube in front of you. That is strong indirect light that is how the test is designed/calibrated.
Will do chemgeek. Will try in the morning at your suggestion and re post. Thank you much.
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