CYA and CH dropping

[kevin.gt]

My CYA and CH have dropped over the past month.

CYA 50 -> 30
CH 275 -> 200

Any ideas why? 20k gallon pool. We have had a bit of rain here in Atlanta and I have an overflow drain at water line. I rarely need to add water from hose. Doesn’t feel like any more than the 1/4” loss to evaporation and bucket test doesn’t indicate a leak.

I will say, both of my bottles of R-0011L seem a little different than my other reagents: one bottle needs wiped between drops and the other produces drops that look a little smaller than other reagents, so perhaps I’m not getting repeatable CH tests? And I’ve always struggled with the subjectivity of the CYA test. Or could that much loss just happen from rain water overflow? I really don’t think 1/3 of my pool water was replaced this month

 

[stevo777]

I’ve also noticed that drops from my R-0011L bottles appear slightly smaller than drops of other reagents. At first I thought it might be a flaw, and questioned the accuracy of the test. But then the drops from a second R-0011L, bought a couple years later, produced similar drops to the first. This is Taylor K2006 kit, with the 0.75 oz reagent bottles.

 

[kevin.gt]

update: I just looked at weather underground and think we may have had 9” of rain here over the past month which might explain it. I have a moderately shallow rectangular pool with large tanning ledge and spa. 9” would be about 6k gallons

 

[mknauss]

Looks pretty normal for some rain overflow dilution.

The R0011L is an indicator reagent. The size of drops do not matter much. Put in enough reagent so that you can easily see the color change.