Sand filter possibly low on sand ?

[PoolDoc]

Test your chlorine with OTO (cheap local test kit w/ yellow/red drops) and tell me what color the OTO turns.

What is your K2006 CYA test result? If it's near 100 ppm, DO IT AGAIN, bu this time test pool water mixed 50:50 with tap water.

[DHoffman]

I don't have a cheap kit on hand, but can pick one up this weekend if needed.
Added 50% tap water to CYA test "3.5ml pool water and 3.5ml tap water" and added 7 ml of the R-0013 reagent and came up with 36 or 37 on the CYA test side.

[PoolDoc]

OK. Just assume 80 ppm CYA, and use the Best Guess chart linked in my signature to set your chlorine levels.

[DHoffman]

Thank you so very much for the help. Water is perfectly clear, impending algae bloom has been stopped in it's tracks. I may have gone overboard on the liquid chlorine to raise to shock level. My FC is 14.5 and CC is still at 0 pump still running 24/7. How often would you suggest that I check my chlorine levels? I plan on leaving the pool uncovered until the temp gets below 80F . Also what would you suggest that a perfect CYA level be to keep chlorine stabile and lasting the longest amount of time? Why on the Taylor kit is the recommended FC 2.0 to a 4.0 if CYA plays such a roll in levels? Did I miss something?

[BigDave]

The Taylor test kit is great. The advice in the book is not. Don't use the book.

[Charlie_R]

As I understand it, and I stress I could be way off base, the Taylor book does not take CYA into account with their recommendations in the book. That would, at least to me, invalidate a lot of what is in that book. A question about that, though. How can a company that makes such an excellent kit not know about something a important as that?

If you want/need to know more, Chem Geek has several posts/threads detailing the relationship, I think.

[chem geek]

See the "Chlorine/CYA Relationship" section in the thread Certified Pool Operator (CPO) training -- What is not taught for more detailed info. Even though this chlorine/CYA relationship was definitively determined in 1974 and known before then (in the 60's), virtually no one in the industry talks about it with any specificity. This is primarily due to "the big lie" from the chlorinated cyanurate manufacturers (makers/sellers of Trichlor and Dichlor) that "CYA doesn't matter; only FC matters".