Carboy of hypo. Put suction tube in with a foot valve to dosing pump then from discharge end of the pump to back pressure valve then to an injection quil in pump header
the water that needs chlorinating should be at 7.2-7.4 ph. use a venturi in the pipeline to draw in the amount of liquid chlorine to treat the amount of contamination in your source water. Better still measure the salt level in your source water , if high enough [over .500 parts/mill] use a salt chlorine generator to manufacture your own chlorine gas in the water flow.
First of all, is this a "Slug" feed or "Intermittent"? Slug feed will need to know amount of water and PPM you wish to achieve. Intermittent I would refer to the answer "underpressure" described with the only addition being, energize the chemical pump when the well turns on or flow in present.