orangepower said:The way we did the math, enough grocery store bleach (gsb) at 8% to raise FC to 30ppm (shock level according to Taylor test kit) would take 7 gallons (around 40$). Or I could have purchased 7 lbs of 70% calcium hypochlorite, with the same effect for $30.
No offense (apparently I came too strong earlier, my apologies), but my pool is 12,500 gallons (so not far off of yours) and my CYA is 70 (much higher than yours), and it only takes me THREE gallons at 8.25% bleach to get to my shock level of 30. So you had to do something wrong somewhere.
Also, have you seen this handy link? A great help when Bleach shopping:
http://poncatechsquad.com/dan/calc/chlorine/
Ace hardware has a great sale going on right now if you have one in your area...4 gallons of 10% for $10.00 which falls into the "GREAT" range on that link.
Walmart brand bleach is usually in the "Good" range on that link also.