Success !

[chem geek]

Friday just before taking 15in of water out 24FC - CYA 65

Sunday after water put back in 11.5 FC - CYA 42 added another 6 quarts of bleach , now pool was about FC 17.5 total or so , did not recheck after adding 6 quarts .

Just for completeness, the 24FC - 65CYA combination has 0.265 ppm disinfecting chlorine (HOCl) while the 17.5FC - 42CYA combination has 0.324 ppm which is not a huge difference. So either the "cutoff" for when a much faster algae kill occurs is somewhere closer to the 0.3 ppm range (rather than 0.5 ppm as I had thought earlier) or you were just hitting the alage hard for a week and it just coincidentally overcame the algae around the same time you decreased your CYA.

The "rule-of-thumb" for hitting a 0.3 ppm disinfecting chlorine (HOCl) level for shocking would be an FC that is about 40% of the CYA level. Still high, but not quite the 50% needed to hit the 0.5 ppm level.

Richard

[Sprocket]

Just thought I would check in again .

All's well this year , we took the cover off on Thus just before Memoral Day and no algae on the bottom or sides but the water had a slight green tint to it .

I added 6 jugs of 6% Ultra bleach and the next morning it was crystal clear and tested 17.5 FC . Vac and sweept the pool that morning and we got in Friday night water was 71 degs and it was HOT out already , felt so good .

Now it's been two weeks and NO PROBLEMS at all . I really feel that lowering the CYA did the trick for my headaches , plus following all your good advice . I seems like the first year I had the pool ( 2 years ago ) .

NO CC this year , yaaaaaaaaaaa . Been runing my FC at 4 to 7 , just add a 3 quart jug when the FC drops below 5 .

I just wanted to give a BIG THANKS <S> to all that run this bb board and for the help etc .

I been trying to stear some people from work here but you know how that goes ? When they find out that they need a good test kit , they start to haze over

Thanks again
sprocket