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I’ve got a reputation around here for being the pool chemistry guru, and I can tell you that nearly every problem pool that I look at has CYA > 100... often times it’s beyond testing.

CYA=Cyanuric Acid
CYA=Conditioner
CYA=Stabilizer

Those three things are all the same thing. Cyanuric acid is the bonding agent in Dichlor and Trichlor, and is needed in pools exposed to the sun. But people keep adding tablets (Trichlor) and powder (Dichlor) and those add more and more and more CYA to the pool, until you can’t put enough chlorine in the pool to kill off the goo (Scientific term for yucky stuff).

FC/Stabilizer table for algae free operation of OUTDOOR pools

Stabilizer . . . . . . Min. FC . . . . Max FC . . . ‘Shock’ FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm
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Raise PH without raising TA - Borax
Raise TA without raising PH - Baking Soda (sodium bicarbonate)
Raise PH and TA - Soda Ash
Lower PH and TA - Muriatic Acid
Raise Calcium hardness - Calcium Chloride
Lower CH - anhydrous trisodium phosphate or drain and dilute
Lower CYA - Drain and Dilute

Trichlor has a pH of around 2 while dichlor has a pH of around 6.
Trichlor is slow dissolving so it is suitable for forming into tablets for use in erosion feeders.
Dichlor is very fast dissolving so it is sold in granular form and is not really suitable for use in erosion feeders.

Dichlor: Adding 1ppm of FC adds .9ppm CYA
Trichlor: Adding 1ppm of FC adds .6ppm CYA
Cal-Hypo: Adding 1ppm of FC adds .7ppm CH