const int  FloatSensor = 5;
const int Relay = 4;
bool prevFloatState = 1;

void setup() {
  Serial.begin(115200);

  pinMode(FloatSensor, INPUT_PULLUP);
  pinMode(Relay, OUTPUT);

  prevFloatState =  digitalRead(FloatSensor);
 
  Serial.print("System started with... ");

  bool initialFloatState = digitalRead(FloatSensor);

  if (initialFloatState == LOW) {
    Serial.println("Water level HIGH & Pressure pump ON");
    digitalWrite(Relay, HIGH);
  }
  else {
    Serial.println("Water level LOW & Pressure pump OFF");
    digitalWrite(Relay, LOW);
  }
}

void loop() {
  static unsigned long lastTime;
  unsigned long now = millis();

  if (now - lastTime < 20) return;    // run loop at 50 Hz, automatic swtich debouncing.
  lastTime = now;

  bool FloatState = digitalRead(FloatSensor);
  if (FloatState != prevFloatState) {
    prevFloatState = FloatState;
    if (FloatState == LOW) {
      Serial.println("Water level HIGH & Pressure pump ON");
      digitalWrite(Relay, HIGH);
    }
    else {
      Serial.println("Water level LOW & Pressure pump OFF");
      digitalWrite(Relay, LOW);
    }
  }
}