A pipe, 900 m long and 200 mm in diameter discharges water to the atmosphere at a point 10 m below the inlet level. With an inlet pressure of 40 kPa gauge, the flow rate is 40 litres/sec. At a point half way between the pipe inlet and outlet, a new tapping is made from which water is taken at a rate of 18 litres/sec. To what value must the inlet pressure be raised in order to maintain the same discharge rate from the end of the pipe? You may assume that the pipe remains full of water and that the average friction factor is not altered by making the new tapping. (ans.: 115.1 kN/m2)