Hello, I have been testing my pool with a TFT100 kit going on three years now. I purchased new test chemicals and everything seemed fine at the beginning of the season. Now when I test the FC I never get above 5 (10 drops). My chlorine is added using a stenner pump and it must be working as the FC has never been below 5 but a few weeks ago it tested at 13 when I first got the pool going. This seemed really odd to me so I let the stenner pump run for 40 minutes and by calculation it should have added 64oz to of chlorine to the pool. I tested before I added ran the pump @ 5ppm and after I ran the pump it's at 5ppm. I am going to do some test's tomorrow to make sure the pump is running as it should but it seems to me that it's staying at 5 for the past two weeks so it has to be adding chlorine. Does anyone have any other suggestions as to what could be causing the problems? Pool has a new liner and was filled with fresh water about a month ago. I used cal hypo powder to start the pool as thats what the installer provided. My CC has been 0 the entire time also. Just wanted to see if anything else could be causing an issue?