const byte P1=13;  // normal pump
const byte P2=12;  // extra pump after 30 sec

int simulateLevel (bool p1, bool p2) {
  // p1 reduces by 4/sec 
  // p1 & p2 reduces by 12/sec 
  // both false increases by 15/sec 
  // random by (-10...10)/sec
  int x = -10 + random(21);
  if (!p1 && !p2) x +=15;
  if ( p1 ) x -=4;
  if ( p2 ) x -=8;
  return x;
}

void setup() {
  pinMode(P1, OUTPUT);
  pinMode(P2, OUTPUT);
  Serial.begin(115200);
}

unsigned int level=800;
bool p1, p2;
unsigned long runTime;


const unsigned int HI = 900;  // switch on
const unsigned int LO = 800;  // switch off
const unsigned long BOOST = 30000; // switch extra pump on after BOOST msec

void loop() {
  Serial.print("775, 925, 900, 800, "); Serial.print(level);
  Serial.print(","); Serial.println(digitalRead(13) ? 899 : 801);
  if (level > HI) { 
    if (p1==false) runTime= millis();
    p1 = true; 
  }
  if (p1 && millis() - runTime > BOOST) {
    p2 = true;
  }
  if (level < LO) {
    p1 = false;
    p2 = false;
  }
  digitalWrite(P1, p1);
  digitalWrite(P2, p2);
  level += simulateLevel(p1, p2);
  
  delay(250);

}