Abstract: Apparatus and method for determining the water content of an oil and water mixture such as is transported by pipelines and which oil and water may vary in density from time to time. A densitometer measures the density of the oil and water mixture in the pipeline and a value for the dielectric constant of the oil is obtained from the density measurement by correlating the density reading with a capacitance or dielectric constant reading from an empirically generated chart. A basal sediment and water instrument measures the dielectric constant of the same mixture. The difference between the two dielectric constants is then obtained. This result is converted directly into a water based percentage by volume of the oil-water mixture being carried by the pipeline.