Chlorine/auto chlorinator

[steq184]

I have a Waterway inline auto chlorinator, i have put the tablets in and made sure they are flat on the bottom, the chlorine level is very high, so I turn the knob down a little, but this does not help, have done this numerous times and the knob is almost in the off position. I find this problem everytime i put tablets in, any ideas, it seems that the chlorinator is a total waste of time to be honest.
regards
Steve