You need to keep the chlorine at shock level(per the Best Guess Chlorine chart) until you can go from sundown one evening until within two hours of sunrise the next day without losing more than 1ppm of chlorine overnight and you also have a CC (combined chlorine) reading no higher than 0.5ppm.

You really need to be able to do your own testing and not have to rely on a pool store. We recommend the Taylor K-2006 or the 2006C which is the same kit but with larger bottles of some of the reagents. You can order it through the Amazon link in my signature below but only order if the seller listed is Amato Industries. Some other sellers are substituting the K-2005 which you do not want.