Hello. I've been on the BBB train for a few months now. I bought the FAS-DPD test and have been keeping the pool at around 7 FC since my CA was around 60 since i previously used the chlorine pucks. The CA has been at 60 for months.
My pool's been looking great but the attached hot tub that waterfalls into the pool had some algae so i decided to shock the whole thing and pour the bleach into the hot tub part since its all an enclosed system.
The night of 5/19 the FC was down to 3.5 and instead of pouring in 1 183 oz jug as i usually do every other night, i put in 3.5 jugs as per the calculator.
The night of 5/20 - 28.5 FC. Did nothing.
Got distracted by a broken shoulder over the weekend.
This morning it was down to 12 so i added 2 jugs as per the pool calculator
This evening it was at 12 again.
I tested the CYA just now and according to the FAS-DPD test, I can still see the black circle when the tube's full to the top - practically 0 PPM of CYA!
What happened? - how did the CYA plummet so much?
PS the hot tub looks fine now for whatever its worth. But i had planned on waiting until it drops less than .5 FC overnight as instructed. Now I dont know what to do.
[EDITED BECAUSE I CANNOT READ A TUBE WITH NUMBERS ON IT]