Lots of rain this winter here in MO. I happened to arrive at my pond this weekend after an overnight rain when the primary spillway pipe was still just barely running in siphon mode. With the water only over the plate about an inch and some waves coming in from the wind, the pipe was sucking in gulps of air and had a nasty vibration/water hammer going on. I could feel it through the ground. I am concerned this vibration is not good for either the pipe or may cause seepage around the outside of the pipe. About an hour later it quit and went into typical water flow down the pipe. Anyone have any experience with this?

I have a typical angled down through the dam pipe with anti-vortex plate over the opening. 8" PVC pipe with 12" wide plate. The top plate is the recommended 1.5 times the width of the pipe - I can certainly put a larger plate on, but there is still going to be some transition point when the discharge goes from siphon mode to standard flow.

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