delayMicroseconds to millis

Projects Programming
4 
const unsigned long waterWait = 4000;
unsigned long waterdelay;

const byte trig = 12;
const byte  echo = 11;

void setup()
{
  Serial.begin(9600);
  pinMode(trig, OUTPUT);
  digitalWrite(trig, LOW);
  pinMode(echo, INPUT);
}

void loop()
{
 if (millis() - waterdelay > waterWait) {
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  unsigned long t = pulseIn(echo, HIGH);
  unsigned long h = t / 45;
  h = h - 5;  // offset correction
  h = 35 - h;  // water height, 0 - 50 cm
  unsigned long hp = 2.7 * h;  // distance in %, 0-100 %
  Serial.print(hp);
  Serial.println(F("%"));
  waterdelay += waterWait;
 }
}

(I hate too much code) This code has not been compiled and it has not been tested.