Sand filter possibly low on sand ?

[DHoffman]

Pool is an Aqua Leader 24' above ground 15,000 gal with a Hayward 1.5 HP pump and 18" sand filter with 1.5" PVC plumbing connections. We were using tabs in a skimmer until about 2 weeks ago, I am not sure if they were stabilized or not. I guess they were because of the CYA level. We figured we would use them up, and our local pool shop said that anything under 120 was just fine when we asked today... Their test results said CYA=95. Thanks for the help.

[DHoffman]

Added about 3" of water to the pool and then we shocked and let circulate for a half hour, then tested FC. Had to add 3 big dippers to get it to turn pink with the 10 ml sample. I stopped adding drops at 40 it was still a strong pink color. I won't add any more tabs to the pool the supply house says "yes of course they have stabilizer in them". And we are using 10% liquid chlorine from the pool supply . Thanks for the help with everything. Will check back a bit later.

[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.