Cant hold chlorine

[herrmanncr]

Think I need to shock to 20 or just maintain 5-10 FC as long as no CC and CYA stays down?

[aylad]

As long as no FC is holding steady, CC stays down and no chlorine loss overnight, then keeping it at normal ranges should be fine. Normal range is determined by your CYA, so here's the guideline...
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

So if your CYA is 65, then 5-10 will be fine--just don't let it get below 5. If the CYA is 100 or greater, then keep it between 8-15 ppm.

If you see CC starting to go up (greater than 0.5 and not dissipated by sun) or the pool starting to look hazy, then shock it again.
Janet