How to make Ultrasonic Water Level Indicator Arduino

const int trig = 2, echo = 3;
long duration, Distanceincm;
void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  pinMode(11, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(8, OUTPUT);
  digitalWrite(8, HIGH);
}

void loop() {
  digitalWrite(trig, HIGH);
  delay(15);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  // The ultrasonic module is placed 20cm above from 1m tank.
  Distanceincm = (duration / 58) - 20;
  if (Distanceincm < 25) {  // Above three quarter
    digitalWrite(11, HIGH);
  }
  else {
    digitalWrite(11, LOW);  // Below three quarter
  }
  //
  if (Distanceincm < 50) {  // Above half level
    digitalWrite(10, HIGH);
  }
  else {
    digitalWrite(10, LOW);  // Below half level
  }
  if (Distanceincm < 75) {
    digitalWrite(9, HIGH);  // Above quarter level
  }
  else {
    digitalWrite(9, LOW);   // Below quarter level
  }
  //Below quarter level, only LED at pin 8 will be ON.
}