Hydraulic and pneumatic power actuators provide automatic control of ball, plug, and butterfly valves, as well as slide gates in water and wastewater applications. This new Manual of Water Supply Practices explains how various actuators are constructed and operated given specific parameters. A valuable resource during startup process and troubleshooting in the field, the manual also describes how to select the best style for the application, and how to install, control, and maintain the actuators. The following types of actuator construction are include: linear cylinder, quarter-turn scotch-yoke, quarter-turn rack-and-pinion, quarter-turn pivoting cylinder, quarter-turn link-lever, and quarter-turn vane. The manual compliments these AWWA Standards: C541 Hydraulic and Pneumatic Cylinder and Vane-Type Actuators for Valves and Slide Gates and C542 Electric Motor Actuators for Valves and Slide Gates, and is intended for operators, engineers, and utility supervisors.