Accurate flow measurement is essential for the management of any type of fluid system. In order for a meter to accurately measure the flow, some installation requirements must be met. These installation requirements are meant to produce a condition where there are limited flow disturbances as the fluid enters the meter. If flow disturbances do occur, the meter may produce inaccurate measurements. This research investigated the effect on accuracy that different types of 12-inch flow meters have as a result of being installed in pipelines of differing inside diameter. The types of meters chosen for this research were the portable ultrasonic meter, the magnetic meter, and four types of differential pressure meters: classical Venturi, Halmi Venturi Tube, V-cone, and the wedge meter. Each meter was tested for accuracy with ten different pipe schedules installed upstream forming a pipewall offset varying between +0.125 inches and 0.937 inches. Ten flow rates between 400gpm and 6,550gpm were considered for each test setup. The meters’ accuracy during each test series was compared to the specified accuracy as defined by the manufacturer of the meter. All results were displayed graphically for comparison. In general, most of the meters tested were affected by the disturbances caused by the pipewall offsets, and some meters were more affected than others. The measurement error was found to be as high as 8% for the ultrasonic meter type. This research demonstrated that for accurate flow measurement, most flow meters require that the inside diameter of the piping be the same as the inside diameter as the meter. Laboratory tests showed that the wedge meter was not dependent upon the upstream pipe installation. Normally, it is recommended that laboratory calibrations be performed to ensure the accurate use of any meter type.