The suction pipe of a pump rises from a sump at a slope of 1 in 5 and water passes through at 1.8 m/s. If dissolved air is released when the pressure falls to more than 70 kN/m2 below atmospheric pressure, find the greatest practicable length of pipe neglecting friction. Assume that the water in the sump is at rest and the water level is 10 m from the base. Assume the density of water to be 1000 kg/m3.