Float switch (water level) with ESP32

Supply 3.3 V Bus GPIO Measures water level

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
1	Output (the part drives it)	D25	To a GPIO with INPUT_PULLUP. Flip the float on its stem to swap open and closed
2	Ground	GND

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

void setup() {
  Serial.begin(115200);
  pinMode(25, INPUT);  // 1
}

void loop() {
  Serial.println(digitalRead(25));
  delay(100);
}

Generic vertical float switch seller sheet, Reed switch inside the stem, operated by a magnet in the float

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.