Hi all, I've been doing a lot of searching and a lot of reading and found answers to most of my questions. But this one I can't figure out.
for at least 6 years+ I and the previous owner knew nothing more about pool care other than throw chlorine pucks in the pool, occasionally some acid and clean the filter. Surprisingly this worked. Never had a green pool. It did have the low PH high TA issue that was very slowly getting worse and I finally decided to work on that when I found this place. That problem is on it's way to being solved now.
But that is where the trouble begins. CYA level after these years was high. Very high. Best guess is 400+ based on the fact that I did a 2/3 drain and fill and now have a CYA of 190. FC back in the pre drain days was 20-30 but again it worked at least for me.
Right now overnight FC loss is less than 1ppm, but total daily loss is 2-3 ppm. Bather load is light to non existent. Only one using the pool right now is the dog. So to state my assumption, 1-2 ppm is being lost to sunlight.
First question is this assumption correct? I am in Arizona and there is very little shade around the pool. It gets sunlight from sunrise to 4pm but is not fully shaded till 6pm+. Figure 12+ hours of direct high Arizona UV sunlight. Pool is also shallow 3-5 feet. So it at least seems plausible to me.
Here is the next question. If I do another drain and fill to bring the CYA to 80-90 for a SWG or 40-50 to keep using bleach what is that going to do to my daily sunlight FC loss?
Is the relationship linear? Am I going to loose 2-4 ppm at a CYA of 90 or 4-8 ppm at a CYA of 50?
Long post I know but wanted to give as much info as possible. Thanks!