JohnT said:
Your alkalinity is fine, but your CYA is too high.
On a separate note, I agree with John but would add "for me" at the end of his statement. Your FC is 5 ppm and this is a little low for 100 ppm of CYA. You have two options:
1 Do some partial draining and refill to lower CYA. Most feel the ideal range is 30-50 ppm.
2. Keep your FC higher, 8 ppm MIN. per the chart below. Stop using Trichlor (3" pucks) and/or Di-chlor (Shock) since both of these add CYA.
Ben's 'best guess' FC/Stabilizer table for algae free operation of OUTDOOR pools
-- as of July 2003 --
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
Quite frankly, there is nothing realy wrong with a high CYA, only as long as you understand that your chlorine must be maintained at a higher level in order to prevent algae and keep your pool properly sanitized. Agian, "I" keep mine lower. Also, as usual, I'll give you the priceless advice of getting a good drop based test kit that utilizes the FAS-DPD Powder system of chlorine testing. Dave S. sells one on this site or you can buy the more expensive Taylor K-006. Either way, do your own testing to avoid being "pool stored" in the future.
Dave