I already have the pump, plumbing, tank and a timer. My question is, can I just connect my pump to a relay in my Pentair easytouch control panel and control the pump with any auxiliary option instead of using the digital timer?
Correct. You put the power to the pump through the relay. Then you can program within the ET the time(s) you want the chlorine pump to run. You should integrate that with the pump relay so it will only run when the pump is running.
It can be added at any time. Spread it out over your normal pump run time, etc. You will find some members add their liquid chlorine in the evening. That way the higher FC level is not reduced by the sun over night.