The Structural Properties of Hexagonal Steiner Minimum Trees for Terminals on the Boundary of an Equilateral Triangle

An irrigation valve comprises a valve housing made from a valve body joined to a valve bonnet by a plurality of attachment screws. The valve body and valve bonnet have an alignment rib received in an alignment notch when the body and bonnet are joined together such that the holes that receive the attachment screws are automatically aligned with one another. The attachment screws have a smooth portion adjacent a threaded portion such that the smooth portion when visible signals to the user that the attachment screws are clear of the valve body but are still captured in the valve bonnet. The valve includes a solenoid that may be remotely actuated to open the valve. An L-shaped actuator arm is also operatively connected to the solenoid for manually opening the valve with the upper portion of the actuator arm being closer to the user than in previous valves and thus easier to grip and turn. Finally, a metering pin in the valve has a flexible mounting which permits side-to-side motion in a metering hole in the valve member to allow the valve to be self cleaning.