What do you use to "sense" flow through your UV unit.

[Bpp124987]

My objective is not to measure how much water is flowing through but to install a failsafe device that would cut off power to the unit should there be no flow.

Ah. In that case though the apex should be fine right? If it’s failure mode is to indicate No Flow when there is flow then you’ll fail safe and just need to clean the apex meter