I was reviewing the recommended levels in Pool School and I've got a couple of questions:
In a plaster pool the chart calls for a CYA level of 30-50 ppm when using bleach, but 70-80 when using a SWCG, yet the recommended chlorine levels are higher for bleach (3-7 ppm) and lower for SWCG (3-5 ppm). The shock level is the same for both given an identical CYA level. If CYA binds usable chlorine, requiring a higher level for it to be effective, shouldn't it be the other way around? Is SWCG chlorine somehow different than liquid bleach chlorine? Can someone explain this to me?
Also, the TA level for the bleach-fed pool is 70-90+ whereas for the SWCG pool it's 60-80 with both types calling for the same pH levels, 7.5-7.8. What's the reason for the different TA levels, and is pH related to TA?
Thanks for any enlightenment,