An elongated upwardly opening trough including a bottom wall interconnecting the lower marginal portions of a pair of upstanding longitudinal side walls and a pair of upstanding transverse end walls. The opposite ends of the trough include water inlet structure and the bottom wall includes a plurality of longitudinally spaced gravity flow outlet openings formed therein disposed generally along the centerline of the trough. Also, the trough includes upstanding longitudinal partition structure dividing the interior of the trough into separate opposite side compartments. One of the water inlet structures opens into one of the compartments at one end of the trough and the other water inlet structure opens into the other compartment at the other end of the trough. The opposite ends of the partition structure are disposed on opposite sides of the longitudinal centerline of the trough and the partition includes a central portion extending transversely of the trough and crossing the centerline thereof. The gravity flow outlet openings disposed on opposite sides of the partition structure are spaced along the ends of the trough opposite to the ends thereof into which the corresponding water inlet structures open. By admitting water into the ends of the opposite side compartments opposite from the ends water is allowed to drain through the gravity flow outlet openings and by maintaining the water level in the opposite side compartments at least slightly above the bottom wall, substantially equal amounts of water will drain by gravity through the gravity flow outlet openings.
