Good morning, @Boone.
You are correct, that the sensor is not going anywhere in the manner that I have it zip tied, which is my preference. The dish does actually have a small lip, maybe 1/4", as well as an opening in the lip where water will start to flow into the dish. I have to say, I found the perfect soap dish for this task. If anyone is interested: Soap Dish
My thought was that vibrations of the PVC would more likely knock the sensor out of the dish and it would fall into the water than a sump overflow would destroy the sensor. So it is a calculated risk, and again only $35, so I am not losing sleep over it. I believe it is much more likely that an early alarm saves me from a flooded basement that would be significantly more costly, time consuming, and frustrating.
Thanks!