I installed this auto-siphon on a small pond last summer. It has worked perfectly until recently. The water went over the spillway and the siphon was not working. Water was flowing through the pipes but the siphon never kicked in. The air inlet valves we not plugged. Any ideas?
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Siphon is either plugged or there is an air leak somewhere to prevent the siphon from starting.
I tried to view the photo but got a 404 error.
I've been studying auto syphons as I am currently installing one. One thing I know from irrigation pump priming is it is hard to know where or if you have a leak. I would try priming the air vent from the top with the smaller ball valve closed. If this doesn't stay as water you have an air vent leak. At your current water level this should remove your air vent from the equation and it should close to full syphon. I've used a temporary syphon a lot to pull down a pond. I've had the temporary one stop for apparently no reason. Upon closer inspection, I could here some air leaking into one of the gaskets and tightening them kept the syphon working. My point is any amount of air leak could cause it not to work. Could you have a crack or tiny leak at any exposed joints? Maybe use shaving cream on the exterior to see. I've done this on irrigation lines.
Is some water coming out of the syphon? Your water level is above the top of the main pipe, syphoning or not, some water should be coming out.
I'm in the process of gluing my air vents on my new syphon. I am using Tpost to support the weight (Those ball valves weigh a lot). Your air vent doesn't have a long run but it isn't supported and anything could bump it and damage the joint. Just an observation as I am doing this myself. My air vent is 2" btw.
Siphon is either plugged or there is an air leak somewhere to prevent the siphon from starting.
I tried to view the photo but got a 404 error.
Hopefully clogged siphons. I need to cut them and put a threaded connection in so I can unclog them. If they are plugged it surely won't be the last time.
In the picture posted, the air break is not covered and the pipe will not enter siphon mode. Lower the vent/siphon air break a couple inches and once the vent is covered, it will go into siphon mode....OR, just close your vent valves to test. If the valves are closed and it will still not siphon...your inlet is clogged.
The reason the air break is not covered is because the pond breached and cut a channel lower than the original level and below the air break.
Neither pipes will go into siphon mode. I built three other ponds with the same set-up and they all work. The only thing I can think of is the pipes are collapsed underground.
Have you been able to check the intake? Maybe bottom was soft and sunk too deep in the mud? You could take a long water hose and run it down your top vents to check for obstruction in the pipe.
What does your air lock look like on the outlet end? Is it keeping air from entering from the outlet?
When it's flowing, but not siphoning, take a small 6' garden hose (or similar), cover one end with your thumb and put the other end up the outlet just far enough to get past the water level standing in the outlet. Once the hose is in there, release your thumb and see if the air pressure releases and starts the siphon.
I had to do this with mine recently. I'm considering a separate one way valve (check valve) at my cleanout (highest point) to let positive air pressure escape easily, but seal once the siphon starts.
The inlets are clear. The end of the pipes are under water in the next pond. They have slide gate valves on the end but it too cold to get in and close them.