// Define variables
int SW_PIN = 5;
int CircPump_PIN = 10;

long lastTimeBeginOn = 0;
long lastTimeBeginOff = 0;
long lastTimeFinishedInterval = 0;
bool CirPumpOldState = 0;

long TimeToBeOn = 5000;//Time the pump will be on iff it has been off for too long
long MaxTimeOff = 10000;//Max time the pump can be off before turning the pump on


void setup() {
  pinMode(SW_PIN, INPUT);
  pinMode(CircPump_PIN, OUTPUT);
}

void loop() {

    // Check if SW_PIN is high
  if(digitalRead(SW_PIN) == HIGH){
    // Turn on CircPump_PIN
    digitalWrite(CircPump_PIN, HIGH);
  }else{
    // Maybe turn off CircPump_PIN if no flush cycle needed
    if(millis() - lastTimeFinishedInterval > MaxTimeOff){
      digitalWrite(CircPump_PIN, HIGH);
    }else{
      digitalWrite(CircPump_PIN, LOW);
    }
  }

  if(digitalRead(CircPump_PIN) != CirPumpOldState){//Detect when the pump changes state
    if(digitalRead(CircPump_PIN)){
      lastTimeBeginOn = millis();
    }else{
      lastTimeBeginOff = millis();
    }
    CirPumpOldState = digitalRead(CircPump_PIN);
  }

  if(digitalRead(CircPump_PIN)){//Detect if the pump is turned on
    if(millis() - lastTimeBeginOn > TimeToBeOn){//The pump has been on for long enough
      lastTimeFinishedInterval = millis();
    }
  }

}