I am starting my first season as a pool owner. I have had a fair amount of chemistry training in college and grad school and I am trying to understand cyanuric acid.
The owners of the pool the previous three seasons were using trichlor tablets, algecide, and some liquid chlorine. I tested the CYA levels at the beginning of the season and they are high, around 60 to 70. So, my plan is to continue using liquid chlorine and to increase the pH (it seems to be very low, like not even on the chart), but NO more trichlor. I should mention, our water is perfect right now. It was crystal clear last season when the pool was closed, and has been the same the past 10 days since opening.
When the pool was first opened 10 days ago the FC levels were testing at 0 and I put in about 10 gallons of bleach. My pool is 28,000 gallons, and I wanted to get the FC level up to about 28 to shock based on our CYA levels (about 60). I tested a day or so after the shock and the FC levels were very high. When I tested again about 4 days later (too long, I know), the FC levels were again zero. So, I added another 2 gallons of 10% liquid chlorine and I am going to test tomorrow.
When you use the daily chlorine/pH test in the "TF FAS-DPD Test Kit," the chlorine test is for FC, right? Meaning if it is testing zero, (i.e. still clear water after adding the drops), then you might have chlorine in reserve with CYA but no active free chlorine? Is that the correct way to look at it?
This is what I don't understand about CYA.... (again, our levels from the previous owners are pretty high, about 60). Why do you need to maintain higher levels of FC at baseline for higher CYA levels if, once you saturate the CYA reservoir, then the FC should be able to do its job? Does CYA really keep a "reservoir" of chlorine? Because if so, then even when the FC levels are testing at zero, I wouldn't necessarily have to put as much FC in to get the levels back up, because there is already a fair amount of chlorine in reserve just waiting to tip out of the CYA reservoir and into the FC "pool" (no pun intended). Is that an accurate way to think about it?
I have not seen a speck of algae in our pool at any point last year or this year (knock on wood) and I really want to keep it that way, but I have no idea how much chrloine I should be adding on a daily to weekly basis in a 28,000 gallon pool with a CYA of 60 (and NOT adding more right now) with minimal use, cool temperatures so far, and moderate sunlight. I honestly don't even know what would be a reasonable range for maintenance chlorine.
Sorry for the longer post. Thank you so much to anyone who takes the time to reply!