Stabiliser/Sunscreen/Cyanuric acid/iso-cyanuric acid/cyanurate/CYA is limited by law in public pools to 50mg/L
If Stabiliser is used the minimum Free Chlorine required is 3mg/L.
See Stabiliser Cyanurate
Why does the Chart on this site seem to condone the use of higher levels?
Why do people sometimes recommend higher levels?
Given the likelihood of errors in testing for Stabiliser (have you ever taken two identical water samples to two pool shops to see how the results compare? - frightening!) it seems to me that no one should intentionally increase stabiliser above 40mg/L under any circumstances.
- About 65% of free chlorine remains after 1 hour of strong sunlight on an outdoor swimming pool without cyanuric acid.
- At a concentration of 10 mg/L of cyanuric acid the loss of chlorine is reduced to about 12%.
- At a concentration of 20 mg/L of cyanuric acid the loss of chlorine is reduced to about 5%.
- At a concentration of 30 mg/L of cyanuric acid the loss of chlorine is reduced to about 3%.
- A concentration of 40 mg/L of cyanuric acid the loss of chlorine is reduced to about 2%.
- Further addition cyanuric acid does not produce any substantial benefit in reduced free chlorine destruction. This follows the law of diminishing returns.
If Stabiliser is used the minimum Free Chlorine required is 3mg/L.
See Stabiliser Cyanurate
Why does the Chart on this site seem to condone the use of higher levels?
Why do people sometimes recommend higher levels?
Given the likelihood of errors in testing for Stabiliser (have you ever taken two identical water samples to two pool shops to see how the results compare? - frightening!) it seems to me that no one should intentionally increase stabiliser above 40mg/L under any circumstances.