    }
   
  }
+ 
+

void loop() {
  delay(1000);
  int uS = sonar.ping_median(15) ; // median filter, error correction 
   distance=(uS / US_ROUNDTRIP_CM); // calculate distance 
   f=(tH-distance); //  calculate fill height of tank
   volume=(Pi*sqr_R*f/1000); // calculate volume of liquid 
       Serial.print("Distance: ");
       Serial.println(distance); // debug 
       Serial.print("Square Radius: ");

       Serial.println(tH);
       Serial.print("FILL Height: ");
       Serial.println(f);
       Serial.print("Formula: ");
       Serial.print( Pi );
       Serial.print(" * ");
       Serial.print(sqr_R);
       Serial.print(" * ");
       Serial.print(f);
       Serial.println(" /1000");
*/
      

   if (distance > 0) { // error detection & hot add
    Serial.print(volume);
      Serial.println(" L");
   } else  {
