Both my (10k gals) and my neighbours (20k gals) pools are maintained at the same levels.
Both our pools are crystal clear, with no algae. Both have SWG.
Because we live on a hill/mountain at a 1000 ft above East Honolulu there is a fair amount of iron deposited into our pools, via trade winds averaging 16 mph, which stain the walls and the surrounding concrete. This comes from the volcanic soil and once a year we use the Citric Acid Method to remove it.
The CyA ppm will drop from 30 to 23/25 over a 3 month period in both pools. This has always baffled us as it is supposed to be constant. He backwashes once every two months and I once a month.
I ran across this link concering the degradation of CyA caused by ferrous sulfate. I realize the solution is not the same and they are using gamma rays, versus high UV rays, or are they interchangeable, but could this have something to do with our larger than normal usage?
http://www.sciencedirect.com/science?_o ... 3eb62b928f
I am not saying it is the reason but there could be a link. Furthemore I also realize that the answer would most probably only be answered by a person with an advanced level of chemistry. So while I hope to get a reply I will also understand if no person wishes to attempt these rather complicated equations.
The pool numbers for his pool look like this, I use borates and have higher calcium,. He does not use borates because of his dogs.
Measured pH 7.5
Total Alkalinity (ppm CaCO3) 60
Free Chlorine (ppm Cl2) 5.0
Cyanuric Acid (ppm CYA) 30
Calcium Hardness (ppm CaCO3) 575
Total Dissolved Solids (ppm) 3,610
Total Sulfate (ppm SO42-) 0
Total Borate (ppm Boron) 0.0
Total Ammonia (ppm Nitrogen) 0.0
U.S. Gallons 10,000
Temperature (oF) 84
Total Chloride (ppm NaCl) 3500
Carbonate Alkalinity (ppm CaCO3) 49.6
Langelier Saturation Index (LSI) -0.01
% HOCl (vs. Total Free Chlorine) 1.5%
OCl- (as ppm Cl2) 0.097
HOCl (as ppm Cl2) 0.077
Calcite Saturation Level (CSL) 0.69
Calcite Saturation Index (CSI) -0.16