A dry pellet dispensing device for installation on a well to chemically treat water drawn from the well. The device includes a pellet reservoir having two reversely inclined floor portions which direct the pellets toward a metering drum. The metering drum is mounted for rotation at an outlet end of the lower of the two floor portions. A plurality of pellet receiving indentations are spaced along the periphery of the metering drum. A drive motor rotates the drum which acts to capture a pellet in each of its pellet receiving indentations. Captured pellets are carried out of the pellet reservoir by the drum and released into a dispensing tube which directs them into the well. The drive motor is controlled by an adjustable interval timer that is responsive to the flow of water from the well. Capture efficiency of the pellet receiving indentations is enhanced by a circumferential indentation centered with respect to the pellet receiving indentations, and by a pair of elongated indentations associated with each pellet receiving indentation on either side of the circumferential indentation and flaring outwardly in a generally V-shape in the direction of rotation of the drum.