Kent: Thanks for your input. There seems to be several views on the elevation to use for when the vent pipe is under water for the syphon action to start. The Pondampiping diagram shows the elevation of the vent pipe to be at the elevation of bottom of the pipe running thru the top of the dam. I admit that your explanation makes sense -ie. the air must be out of the pipe for the syphon action to start; but, if I could get the syphon action to start at a lower level, say at the elevation of the bottom of the pipe running thru the top of the dam, it would allow the syphon action to run longer and obtain a lower water level.
Does anyone else have a comment on the elevation of the vent pipe with respect to how it allows the syphon action to commence?
