Poolsean,

the old Pure&Clear "wall mounted" was actually mounted over a pump return outlet , so it did have flow thru it. One problem was that it had to have a limited flow - my system has a valve to control flow out that particular outlet. It has a pump sensor (magnetic, I think) and looks to have had an option for a flow sensor as well.

Regarding plastic piping - I was referring to the chlorine itself, in somewhat "high" concentrations downstream of the cell, degrading the pipe, resulting in "stuff" coming out into the pool