1. The problem statement, all variables and given/known data A water manometer is connected to the wall of two pipelines in order to measure pressure difference between the pipes. Manometer shows a 0.5m height difference, pipe B is 3m higher than pipe A. Find pressure difference between pipes. [PLAIN]http://img191.imageshack.us/img191/9528/fluid.jpg [Broken] Density water: 1000kg/m3 Density Oil: 850kg/m3 2. Relevant equations Pressure difference = density of fluid x height difference x 9.8 3. The attempt at a solution From the illustration it is evident that pipe B will have lower pressure than pipe A since the oil pressure in pipe A can depress the water in manometer to a certain height even as Pipe B is mounted higher than pipe A. If the two pipes were located at the same height, the manometer alone would show the true pressure difference: Pressure difference manometer = 1000 x 0.5 x 9.8 = 4900 Pa Since pipe B is mounted 3m higher than pipe A we need to add this pressure difference: Pressure difference altitude = 850 x 3 x 9.8 = 24990 Pa Total pressure difference is the sum of these two: 24990+4900 = 29890 Pa. The correct answer is 25751 Pa. My reasoning must be wrong somewhere?