Quote Originally Posted by hannadock View Post
I must have made a typo it is 56000 if calculator is correct. 20X40 with 8.5 deep end.
If your pool is "typical" -- 3.5 feet shallow end, 8.5' deep end... the average depth is close to 6 feet.

20 x 40 (rectangle) x 6 (avg. depth) x 7.48 (gallons in cubic sq ft) = 35, 900 gallons

It appears Total Alkalinity (TA) went from too low to too high. You may be trying to do too many things at once. Do you have a test result for Calcium Hardness (CH)?

With a CYA of 70 ppm, you must maintain AT LEAST 20 PPM Free Chlorine (FC) to continue shocking...

See http://www.poolforum.com/pf2/showthread.php?t=365