0http://math.stackexchange.com/questions/946493/solve-for-pressure-drop-across-and-orifice# [Broken] I'm running 1/2" pipe but the only way to connect a 9/16" flow switch is with a 1/4" adapter. I'd have to go from 1/2" down to 1/4" to the 9/16" flow switch down to 1/4" back to 1/2". I was wondering if this would cause a large pressure drop but I used this online calculator and was wondering if anyone could verify these numbers: Calculation output Flow medium: Water 20 °C / liquid Volume flow: 2 l/min Weight density: 998.206 kg/m³ Dynamic Viscosity: 1001.61 10-6 kg/ms Element of pipe: Orifice sharp-edged Dimensions of element: Diameter of pipe D1: .5 in. Diameter of pipe D2: .25 in. Velocity of flow: 0.86 ft./s Reynolds number: 3330 Velocity of flow 2: 3.45 ft./s Reynolds number 2: 6661 Flow: turbulent Absolute roughness: Pipe friction number: Resistance coefficient: 30.68 Resist.coeff.branching pipe: - Press.drop branch.pipe: - Pressure drop: 22.14 lbw./sq.ft. 0.15 psi I've also looked at a flow rate calculator and was wondering if the down size in the piping would affect the flow rate substantially? I'm really trying to stay at 2L/min.