The method of valve operation where:
DROPWEIGHT: A valve that is closed by the action of a weighted lever being released, the weight normally being prevented from dropping by being held by a wire, the closure normally being made by the action of heat on a fusible link in the wire FLOAT: A valve that is opened and closed by the action of a float that rises and falls with water level. The float may be a ball attached to a lever or other mechanism HYDRAULIC: A valve that is opened and closed by hydraulic actuation LEVER: A valve that is opened and closed by the action of a lever rotating the gate within the valve. LOCKSHIELD: A valve that requires the use of a special lockshield key for opening and closing, the operating mechanism being protected by a shroud during normal operation. MOTORIZED: A valve that is opened and closed by the action of an electric motor on an actuator PNEUMATIC: A valve that is opened and closed by pneumatic actuation SOLENOID: A valve that is normally held open by a magnetic field in a coil acting on the gate but that is closed immediately if the electrical current generating the magnetic field is removed. SPRING: A valve that is normally held in position by the pressure of a spring on a plate but that may be caused to open if the pressure of the fluid is sufficient to overcome the spring pressure. THERMOSTATIC: A valve in which the ports are opened or closed to maintain a required predetermined temperature. WHEEL: A valve that is opened and closed by the action of a wheel moving the gate within the valve.