is CYA 90 w/SWG OK?

May 26, 2014
44
St Louis, MO
I have been gradually adding CYA, as per Pool School, to get up to 70(SWG). June 5th was 50, added more, June 12th was 60, waited a few days then added as per Pool Math. Today is 90. I know the recommendation is 70-80, is 90 too high? Will it lower on its own? Should I adjust FC? It is currently 4. Thanks
 
With CYA at 90 and a SWG you never want to let FC go below 4. It is best to have some safety margin, so yes you should probably increase the FC level a little.

CYA at 90 isn't the end of the world. It will tend to go down very slowly over the course of a swim season.

It is best to give CYA a full week to dissolve and show up on the test. Testing too soon can give you an incorrect, lower than actual, reading.
 
At CYA levels that are only a little too high, the main risk is needing ridiculously large amounts of chlorine should you ever get algae. As CYA goes up further additional problems appear. For example it is essentially impossible to know what your CYA level actually is when it is above about 180.

I would raise FC to 6. 5 is OK, but 6 feels safer given the problems you will have if you do get algae.
 
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