Detecting floods using water sensor : https://help.sinric.pro/pages/tutorials/custom-device-types/water-sensor/flood-leak-rain-sensor.html

detecting-water-level.ino

#if defined(ESP8266)
  const int sPin = A0;  
  const int vccPin = D2;
#elif defined(ESP32) 
  const int sPin = 34;  
  const int vccPin = 17;  
#elif defined(ARDUINO_ARCH_RP2040)
  const int sPin = 26;  
  const int vccPin = 6;  
#endif

const int SENSOR_MAX = 560;
const int SENSOR_MIN = 1;

void setup() {
  Serial.begin(9600);
  pinMode(sPin, INPUT);
  pinMode(vccPin, OUTPUT);
  digitalWrite(vccPin, LOW); // turn off the sensor at the begining.
}

void loop() {
  digitalWrite(vccPin, HIGH);         // turn on the power for sensor.
  delay(100);                           // wait 100ms
  int value = analogRead(sPin);   // make a reading from sensor
  digitalWrite(vccPin, LOW);         // turn off the sensor
  
  int waterLevelHeightInCm = map(value, SENSOR_MIN, SENSOR_MAX, 0, 5); // Map sensor value between 0..5 levels (1 cm = 1 level)
  Serial.printf("Water level: %d\n", waterLevelHeightInCm);  // print reading

  delay(1000);
}