I have lurked this site for a while and finally got fed up hearing about the conflicting advice my mother was getting from pool stores. Order the TF-100 and drove over to get some readings.
30,000 gallon vinyl pool.
FC = 0
CC = didn't test
PH = 6.6
TA = 40
CYA = 80
The pool water is clear, but there are a few small spots of what appear to be black algae forming on some liner seams and there is some sporadic yellow staining on the liner and white stairs. I decided to bring the pool up to shock level and according to the pool calculator that is 21ppm given the CYA of 80. The bottles of bleach I'm using are 121oz @8.25% and the calculator called for 962oz (7.9 bottles). I just rounded up to 8. I should add that I brought the PH and TA levels back up 1st before I dealt with the chlorine levels.
I added the bleach at 11pm last night and didn't get around to retesting until 11am this morning and I am very surprised (and confused) with what I got for chlorine numbers. I ran the chlorine test a 2nd time to reconfirm these numbers.
FC = 2.5
CC = 9.0
PH = 7.5
TA = 100
CYA = 80 (carried over from 1st test)
Am I doing something wrong here? I added 968 ounces of 8.25% bleach and it didn't raise the FC number to the shock level of 21 that the pool calculator suggested it would. Is it normal to have that much burn-off overnight? I'm going to buy out Walmart's bleach supply at this rate since it is my understanding that I need to get up to shock level and maintain it there until that CC level comes down to zero.
P.S. Not sure if I posted this in the right spot so please bear with me if I didn't.