CNK, The answer to your question is a MIN of 1.5 If your pool has a CL level lower than 1.5 then it is not safe to swim in. The NSFP reg book shows this year for 2006 for CL levels to be between 2.5 and 7.5. Your CYA should not go over 100 PPM. the only way to reduce this level is to drain water off the top of the pool and replace with fresh water. There is no chemical to reduce CYA in a pool. CYA stays at the top 3 inches of the surface of the pool on a calm steady day. Draining from a skimmer or a scum ledge is the best way to lower CYA if it gets too high.