Pond Boss Forums INTRO Questions & Observations Pond siphon startup question

Good news, the wayward pond is now officially full.


Water is coming out of the 8” outflow in a steady stream


The vent is at least 3 inches underwater and tee plug is tight.


My question is why isn’t the high flow siphon mode firing up? Does the water have to get higher for flow to reach a tipping point?

Done some research over the weekend and I think I found a possible explanation. In my crude drawing below, the system will start to outflow when water level hits point A (lower lip of pipe). As the water rises the flow volume will increase and point B (vent tube opening) will be covered, but siphon action will not start. When water flow hits point C (the upper pipe edge) siphon should start and continue until Point B is exposed to the air, breaking the water seal.

So it is very likely there will be substantial flow through the system without the system going into siphon mode. It should go into full siphon mode only during extreme rain events with large water level fluctuations.

Is my understanding now correct?

I need to build a set up like this. Let us know when it works.

I'm not familiar with that kind of siphon but I think your assumption could be correct.

It might not need to get to C before it starts the siphon. If the flow gets going fast enough it may pull up enough water to fill the pipe and then the siphoning would start.

Review this explanation of the bottom withdrawal siphon system (note its points are labeled differently than your drawing):

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

It states point B should be at least one pipe diameter lower than point A. Also C should be at least 4' below E.

Does your system meet this? If not I suspect your pond will need a higher "flood" to activate the full siphon mode. More air trapped in the top of the system will have to be "sucked" down to go into siphon mode.

And yes, the majority of the year the pipe will be running in "standard" mode. Just during peak heavy rain events it will run in siphon mode.

First I would like to say I do not have a drain like this and I am not an expert. But what I read on this sight I thought the pipe went straight threw the dam not up and over. The way your picture is you only have a small % of suction, the exit pipe is only a little lower than the inlet pipe. Suction should start when water covers the air pipe B. Again I may be wrong.

Red - I wasn't there the day they installed the siphon system, but the local NRCS agent was. I've always wondered if they put the drop in the pipe over the dam to the outflow. I think I might fish a small level down my 4" vent pipe and use my flexible snake camera to see if there is any tilt. I have a substantial vertical height difference between intake and outflow, at least 20 feet.

Nehunter - I have seen that style of water control setup. Though if the intake is near the bottom of the pond, the outlet has a manual control valve were it exits the dam. Then you lose the automatic start and stop action. A slanted pipe through the dam with the inlet set at normal pool height would function as a type of siphon also, but you lose the ability to draw water from bottom of the pond. The over the top style gives you automatic regulation and ability to draw down if you desire with drawing water from the low O2 zone.

Ok I was was wrong, I for some reason thought the water level was some where between A and the inlet to give it more storage before it started to drain. Could you drop air vet pipe 2 feet lower than point A. So when it would start to draw it would not stop tell air is let in 2 feet lower. So a system like this could be put in on a old pond with out cutting dam to or bellow water level.

I like the idea of the horizontal pipe being higher than the after siphon lake level, but wouldn't the low flow drainage (and most common) state only resume when the water level reached the height of the horizontal pipe (point A) resulting in a pretty wide range in lake levels?

1)Did you build the siphon?
2)How well has it worked?
3) How great a risk is it that the vent inlet at point F got plugged while unattended and the siphon went all the way down to the main inlet level?

Thanks,
David - Dallas