Hi all,
I'm also looking for a way to monitor holding tank levels. There are several monitors that use capacitance sensors that connect to the outside of the tank. Here's an example:

https://tankedge.com/products.html

Has anyone tried these?

Does anyone know the thickness of the tank walls?
Are they solid fiberglass?

Here's another suggestion that involves screws through the walls:
"I put small stainless steel self-tappers through the side at strategic levels and then used the conductivity of the contents to feed a small amount of current to transistors which in turn switched on LEDs."

Any other ideas?

Thanks for any ideas.
Kent
SM 243
Kristy
Ft Lauderdale, FL USA