Question: Two water tanks, open to the atmosphere, are connected by a pair of parallel pipes each having an inside diameter of 2.5 cm. The pipes are 20 m long. One is a "smooth" tube, but the other is a galvanized iron pipe. What must be the elevation difference for the two tanks in order for the total flow rate for the two pipes to be 1.00 kg/s? (Neglect entrance and exit pressure-drop effects.)