CYA testing...and the black dot magic trick

Killer01ws6

Gold Supporter
Mar 2, 2021
5
Panhandle of FL
Pool Size
21998
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Glance at the dot. When you don’t see the dot you are done.


As much as possible you should do the CYA test in the same consistent light conditions:

  • Outside in full sun or use the brightest indirect indoor light that you can if you have to test at night
  • Back to sun
  • Don't stare at the dot as you pour
  • Fill to a line, hold the tube waist high, and glance at the dot
  • If you see the dot fill to the next line and glance at the dot
  • When the dot disappears you round up to the previous line. If you saw the dot at 40 and not at 30 then you call it 40
THIS... is the best explanation I have seen in my short time of figuring this out. I have had flux readings myself and never sure why.. I do all of what you say, but I do stare at the dot, even have it go away, then look harder and see it, start adding more water then wonder why I am at 50 again haha..

Tnks for the clarity on my cloudy little CYA bottle heh.
 
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ralphsyv

Gold Supporter
Sep 27, 2020
121
Daytona Beach, Florida
Glance at the dot. When you don’t see the dot you are done.


As much as possible you should do the CYA test in the same consistent light conditions:

  • Outside in full sun or use the brightest indirect indoor light that you can if you have to test at night
  • Back to sun
  • Don't stare at the dot as you pour
  • Fill to a line, hold the tube waist high, and glance at the dot
  • If you see the dot fill to the next line and glance at the dot
  • When the dot disappears you round up to the previous line. If you saw the dot at 40 and not at 30 then you call it 40

THIS... is the best explanation I have seen in my short time of figuring this out. I have had flux readings myself and never sure why.. I do all of what you say, but I do stare at the dot, even have it go away, then look harder and see it, start adding more water then wonder why I am at 50 again haha..

Tnks for the clarity on my cloudy little CYA bottle heh.
Yes! CYA can be tricky to determine. It's because of persistence of vision (when you stare at something 30 seconds, it's fixed in your eyes). Thanks, @ajw22 !!!!!!
 
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