Latest chem tests; CYA went down?

[300winmag]

Just did my weekly full chem test, and my CYA went down. I thought it was very hard to get CYA out of the water, without removing water...is that not the case?

FC: 4.5
CC: 0.0
pH: 8.0
TA: 60
CH 340
CYA: between 40 and 50.

pH crept up because I had to add salt yesterday, and left the spa spillway on to help agitate the water. Probably not needed, but that's OK.

I'll treat all accordingly per pool math, just curious if the CYA decrease is normal. EDIT Does it go down with evaporation, or does it act like salt and never leave unless water is removed?

Thanks

 

[300winmag]

I am going to answer my own question... My bad, we just had a baby and I'm sleep deprived.

While at the hospital for the delivery the auto fill got stuck filling. Surely it displaced enough water to lower the CYA.

Not even sure who turned it back on, but I HATE it. Just permanently discnnected it.

 

[ping]

CYA will slowly drop throughout the year and will need to be topped off every now and then. In your case, lesson learned.