16 x 32, 19,000 gallon pool. I am using trichlor and shocking with non-chlorine shock. Pool is clear, pump is running well. Numbers are within range on Ph, Alk and Stabilizer. Chlorine is not registering. Thought it was the test strips, replaced and still came up with the same results. I have never had this problem before. What should my next course of action be? I have never taken a sample to the local Leslies thinking that the results will always be skewed towards their liking. Switched back, last year, to trichlor after a couple years of using Liquid chlorine. It was cheaper and it seemed more stable and reliable. I started using the non-chlorine shock last year also. Thought it complimented the trichlor well. Do I need to initially shock with chlorine (liquid or otherwise) to get things going?