Abstract: A hydroseparator for separating particles based on the differences in settling rates such as for separating fly ash from gypsum includes a substantially cylindrical side wall closed at its bottom end by a floor. A laminar upflow is created through the hydroseparator by adding dilution water to the bottom of the hydroseparator and removing most of the added dilution water from the top of the hydroseparator. The remaining volume of liquid is removed in an underflow. The hydroseparator is divided into at least two sections by a baffle that extends about the interior of the side wall. An inlet is disposed in the center of the hydroseparator slightly above the baffle such that the material added to the hydroseparator to be separated is inserted into the section of the hydroseparator completely surrounded by the baffle.