Pond Boss Forums POND CONSTRUCTION Building a dam Siphon Vent Question

Can someone explain to me how a vent works on a siphon system?

A vent completes the siphon either breaking the suction by allowing air into the system (when opened) or lets air out of the pipe when filling (then close vent) and start siphon.

c.j., a vent is also called a siphon break....once the vent opening is covered, your siphon starts, when water is lowered and allows air into the vent opening, the air "breaks" the siphon. Without a vent to break the siphon, the water would lower until air enters the siphon inlet and no more water can be drained.

https://i.imgur.com/o1ek5jf.jpg
Does anyone think you could install a single pipe siphon system like DC70 did on his buried double siphon with a single vent in northern climates? I believe he might be onto something. Instead of using 2 siphon pipes with one vent, could you setup your system using one larger siphon pipe with one vent with trash rack type holes drilled that extends into a larger sock pipe covered with rock in the pond? This way when the water rises in the larger sock pipe that your smaller vent pipe with holes drilled to the height of the apex in your siphon pipe is reached the siphon is created. When the water recedes to the holes you drilled in the smaller vent pipe the siphon is broken. The image posted above got me thinking. All of the piping would be buried according to your local frost line. It might be that you don�t use a sock pipe and use apiece of solid pipe that extends a couple of inches above the apex of your siphon pipe to prevent water from getting inside the dam. A 2 inch vent pipe with holes using an adapter inside a 4 inch pipe buried in rock in the pond. Thoughts or Suggestions?
Heppy

The original thread is #482496 - 11/11/17 11:07 AM Automatic syphon system in northern climates by DC70. I�m not sure how to copy a thread and put my original comment in a new post. Any help is greatly appreciated.
Heppy

On DC70 siphon system how does it get air? It looks to me it would be all under water or covered with dirt.

He said �Not pictured is the 18 inch piece of culvert pipe I put over this that acts as a pit. I ran a 4 inch piece of pipe to the surface with a grate flush with the ground for the air to enter. I also capped the pit with a concrete cap and covered it with dirt and grass.� I�m assuming he capped the pit containing the the siphon pipes and vent pipe and ran a 4� pipe from the pit to ground level. Do you think this could be done with a single siphon pipe and vent pipe being completely buried without having a pit and relying on the amount of air contained in the vent pipe above the apex of the siphon pipe? Wouldn�t there always be available air in the vent pipe without having a pit? If you positioned the 2� vent pipe higher than the siphon pipe drilling holes in the 2� vent pipe from the apex level of the siphon pipe and extended it approximately two feet through a 4� adapter that then attaches to a 4� piece of pipe. The 4� pipe would be in the pond covered with rock and the water level would rise through that piece of 4� pipe until it reached the 2� vent pipe with holes drilled into it until the water met the highest hole at the apex of the siphon pipe. Would this not then create a siphon that was broken only when the water level receded below the holes at the apex level of the siphon pipe in the vent pipe? The 4� pipe would be higher than the apex of the siphon pipe. This maybe a little bit confusing but all of the 2� vent pipe with holes would be encased inside the 4� pipe using the adapter. You would still have solid 2� vent pipe coming from your tee in the siphon pipe until it reached the adapter. Isn�t there always air in the siphon pipe when it is not in siphon mode?
Heppy

Not sure I follow your design so I best not comment. But here is another explanation of operation of a bottom withdrawal system:

http://www.georgialandsales.com/pdf/PondSiphonSystem.pdf

I chose to go with a standard primary spillway pipe with hood on my new pond.

Redonthehead, the siphon would be the same as in the link you provided. The only difference would be that the entire system would be completely buried below the frost line in your location. The downward end of the vent that will reach the water in a siphon control in the picture would extend inside a larger piece of pipe that is higher than the apex of the main siphon pipe. An adapter (example 2� pipe to 4� pipe adapter) is also higher than the apex of the siphon pipe would allow you to have the smaller pipe inside a larger pipe with holes drilled in the smaller pipe up to the point it reaches the apex level of the siphon pipe. The solid larger pipe would extend underneath the face of the dam before coming out into the water side face of the dam (trash rack on the end of the larger pipe???) that would then be covered with rock to allow water not debris to rise and fall in the larger pipe as the water level rises and falls. The holes in the smaller pipe inside the larger pipe would control when the water siphons and stops. I was thinking this might be a solution for those in northern climates and was looking for feedback from others with experience that could advise me one way or another. This is just an idea that I thought of recently. Thoughts? Everyone please feel free to critique my idea so that we might find a viable solution for others who live in northern climates.
Heppy

Addendum: I�m also inclined to think that if you had a 6-8 foot solid vent pipe in the pond, you could expect that in some worst case scenario, this would also serve the role of an emergency siphon break without fully draining your pond. ???
Heppy