Pressure Gradient? Water (=1.94slug/ft3;= 2.34105lbfs/ft2 ) flows at 10gpm (gallon per minute) in a horizontal 0.75-in-diameter pipe (galvanized iron; 0.0005-ft roughness). Determine the pressure gradient, p/L, along the pipe. [1 gallon =77/576ft3.] Ans. 0.210psi/ft