A control device for a siphon tube regulates the
liquid ?ow through the tube to provide self-priming for the
tube and a level control for the liquid supply to the tube. The
device includes a valve at the tube outlet and a valve actuating
mechanism constructed and arranged to change the valve
setting in response to a predetermined liquid level at the tube
inlet for alternately stopping and starting the liquid ?ow
through the tube. When a lower liquid level at the tube inlet is
reached, the valve is moved to stop the ?ow and trap a column
of liquid in the tube and the valve is moved to release the
column to prime the tube at a higher liquid level at the tube
inlet to start the ?ow through the tube.