I’ve done something similar with my fuel oil tank, except I’ve got an ultrasonic sensor threaded into my inspection port. It’s connected to a PoE powered ESP32. And now you’ve got me really concerned that even though I’ve got two compartments on the case (which itself is shoved inside a PVC pipe), I should probably do more to move the PoE powered ESP further away.

All that so I can be sure I have enough heat on really cold days or if the power goes out.