I am currently trying out some new stormwater management design software(HydroCAD) to layout a new wet pond. One of the options for the outlet structure is a siphon. With this option it calculates 0 flow until the siphon starts and 0 flow after the siphon breaks. This is what I need to achieve the proper outlet flows.

The problem is I can't find a siphon that works this way in this application. All siphons that I have seen have trickle flow until the water level rises sufficiently to start the siphon. I have used a bell siphon made by Fluid Dynamics in septic applications that discharged water like I need, but they were part of the septic tank and I don't think they can be adapted to this application.

I'm sure I could construct something that would work, but would prefer a commercially available product to save time. Anybody aware of any products out there like this?

Thanks