I just over a month ago added a 7.5 gallon tank and Stenner 3gpd pump. I have changed from Clorox to HDX Chlorine after Sam's Club ran out. My chlorine level keeps bouncing day to day. Over the last week 5.5, 2.5,4.5,4,4.5,4.5,0,9 all taken just before dark. I changed poolmath from 6% to 10%. I divide the oz of chlorine by 16 to get my pump run time. I run my pool pump for an hour or more after the chlorine pump. I do not understand why it is so inconsistent when before doing it manually the changes were more minor and could attribute to a hotter day or if people had used the pool. If my math was wrong I would think I would be consistently low or high. I leave the variable stenner on high and just adjust the clock that runs it. I went to running from midnight to 2,3,and last night to 8am. The math for time is an excel chart so my /16 is the same. Twice The R0870 DPD power has not turned the test water red pink just stayed clear that is what I call 0. The only thing I can see is if some times if the Phoenix is in the shallow end then I might not be getting good mixing of filtered water and non filtered water. BTW I did also just go to HDX pool acid found it was 14% instead of 32% so I will most likely go back to Leslie's for acid.