Problem with liquid chlorine and pool calculator


Bronze Supporter
Jul 28, 2019
Lakewood, New Jersey
i hope i'm not too late to add to this thread. so it seemed that while my chlorine use was high, it was possibly within the range of normal. the issue was that my FC levels should be between 7-9ppm for my cya of 60 and never drop less than 5 and adding 1 gallon of 12% chlorine, i kept losing at or below 5 by evening (i started at about 10 after adding a gallon). so i figured i'd just have to add 1.5 gallons one day to get it to more like 13ppm so by evening it was 7ppm.

I did this last sunday morning - put in 1.5 gallons of chlorine (and over an $8 cost) and by evening, to my frustration, it was at 4.5 again!
i thought i was losing my mind. So monday morning i figured i'd try again. Same thing happened! so instead of using 5-6ppm, i was using like 7.5 ppm.

1) Does this make sense? this would cost me $1k+ in chlorine for the season or 10 times what i used when using tabs!! i threw in the towel and monday night put in tabs. for the first time this season my chlorine test comes in at 7-7.5ppm at all times - morning and evening.

2) according to everything i read if i continue to use tabs my cya will go up. but for years i used tabs before i knew anything about the science i learned on this website. i used a regular pool test strip for years and the cya color was always in the "ideal" range box of 30-50ppm. i used tabs the whole season and never saw it moved from that color. why?

Lei Mend

Jun 4, 2020
ok all. i tried again with your encouragement that the pool math HAS to work. originally i added once pump went on (about 9am) and it was sunny, so i was losing chlorine as i was adding. I got my pool paperwork and changed volume of pool the the exact 21,480 gallons on the calculator. 121 oz should raise my chlorine from 4.5 to 10ppm. 1 gallon DID raise my chlorine from 4.5 to 10 on June 15th, 16th and 17th. at end of each day it was back to 4.5. yesterday was cold, no sunshine and rainy at times. at end of day it was 5 or 5.5.

So in general i am indeed using 5.5ppm of chlorine daily - or an entire bottle. I am back to one of my original questions - this is prohibitively expensive. more than 3 times what i've ever paid for chlorine. Why am i using liquid?
hey! you’re not the only one. we have 24,000 Gallons oval pool that gets direct sun from 11am to 6pm. I’m also new to using Liquid Chlorine. I buy 12.5% from the pool store at $5.50 per gallon. I can’t find chlorine anywhere else.

Today I lost about 9ppm between 9am and 5pm. My CYA is 60. I know I need to keep a daily record to make a better observation. I switched from using 3in chlorine tabs because my CYA was 157 last month and I had to drain more than half of the water and refill.

Anyway, I know I won’t be able to keep up with using Liquid Chlorine for daily sanitation because of the cost. I will use Liquid Chlorine for the SLAM process because it is easier to handle than the shock powders and also cheaper than Cal Hypo. I think it will be more cost effective for me to drain some water again to get to 40-50CYA level then use the tabs.
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