I have read the info on
this page. Note, in section 3 it requires a 1.0-3.0 chlorine residual for a few days until the ionizer gets up to speed. Then, in section 6, it recommends shocking the pool on a weekly basis or more if needed. And you are supposed to use algaecide if you start to see algae.
They also recommend 0ppm of stabilizer or CYA in the pool. That means the pool will have to be drained and refilled before installing the system to get the 0 CYA level if you have any CYA in the water. However, they also recommend shocking with dichlor, which adds CYA to the pool. If your cousin follows these instructions to the letter they will be draining the pool on a regular basis.
By the way, a weekly dose of shock is the standard pool store recommendation for a chlorine pool. Your cousin will be using just as much chlorine with the Power Ionizer as someone who follows standard pool store recommendations and didn't shell out a couple of hundred bucks on the power ionizer system.