Richard320, thanks...my problem is not age, unfortunately it's comprehension...you're right the lines are very close together. Yesterday I put it at 100 with my k2006, took a sample to the pool store and they got the same. Checked again this am, after a 3" thunder boomer last night and it was reading between 90-100. I'm in the midst of draining about 2500 gallons. Thanks for the tips, I didn't think about the salt and FC. Probably should rent a pump....this is too slooooow!