Abstract: A valve mechanism for a livestock watering bowl. The valve mechanism is mounted in a water inlet line in the bowl and is adapted to be actuated by an animal to control the flow of water into the bowl. The valve mechanism includes a body provided with an inlet connected to the water line and having a central chamber connected through an inlet passage to the inlet. The inlet is adapted to be opened and closed by a valve member carried by a plunger that extends axially through the inlet passage and the central chamber and terminates in a button that projects outwardly from the opposite end of the body. The portion of the plunger located within the inlet passage has a non-circular cross section to provide a clearance between that portion of the plunger and the inlet passage, while the portion of the plunger located within the central chamber is formed with a laterally extending shoulder.