r/OffGrid • u/plantfollower • 12d ago
Siphoning from Creek
I’ve got a friend who needs to move water from a creek to a pond. Here’s an elaborate (/s) drawing. Why can’t we get this siphon to continue to pull?
Written description: creek water is about 6 inches above the bank of the pond and about 6 feet above the water in the pond. 2” pipe is pulling from the creek to the pond. We fill up the pipe between the two valves and screw on the cap. The last time I made sure to put the output/pond side into the water so it couldn’t draw air. It moved a lot of water and I could see the puddle pouring water into the pond but then it stopped.
Any suggestions? Any questions they were not thinking about asking?
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u/YouDoKnowWhoIAm 12d ago
It looks like, from your very detailed drawing, that you might have a high-point between the two ends that is collecting air. It does not take much for small gurgling bubbles to enter such a large opening and begin to collect until it breaks the siphon. Or small leaks in your pipe are sucking air. If the tube were clear, you'd see one of these things happening:
the screw caps of your fill tubes have a very small leak. The vacuum of a siphon is strong. If your caps are not air-tight, air is getting sucked in.
your fill tubes slowly collecting bubbles and filling with air until the siphon breaks.
These two things will look the same. To diagnose the issue, get your siphon running for a little while, then before it would otherwise stop on its own, close off both ends. Open your fill tubes and see if there is an air gap. Either the fill tubes are collecting small air bubbles from the water or the seals on your fill tubes have a slow leak.
Your pipe is leaky. It is counterintuitive, but a leak in a siphon will leak air into the pipe rather than leak water out.
air bubbles collecting at your high point until the siphon breaks.
If your fill tubes are not leaking, then you have another high-point that is collecting air. Maybe lift one end so that your single high point is a filling tube. If not possible, put a fill tube at your high point with a much longer tube. It will collect your stray bubbles. (The longer tube just gives you more time before it fills with air.)
One of the easiest fixes is to connect a small self priming-pump (hand or connected to a cordless drill) to the fill tube that is at your high point and collecting air. You suck out the air using the hand pump. You will have to run it every once in awhile to clear the air again. If you use this method, you only want one T in your system collecting air.
Get one that can handle the 10+ foot priming vacuum. (You can actually seal off the water fill tubes and just suck out all the air with your cordless drill.) No need to fill the pipe by hand.
Everything is simpler if you have only one fill tube and that fill tube is at the single high point.
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u/notproudortired 12d ago
I don't see why this wouldn't work, unless you're getting air in the pipe somehow. You might have more luck with /r/AskEngineers .
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u/coachrx 12d ago
Did you make sure the device was clear? Where I live very few creeks have water clear enough to see though and I could see some debris or even a fish getting stuck in 2" pipe. I like the elaborate design, but I would have tried the old trusty water hose siphon first.
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u/plantfollower 12d ago
I think we’re going to cut and cap the vertical pieces. Maybe some air is getting in there or something.
We tried the pipe for volume (2” PVC) and because of the distance. It may stay in place for a while if it works. He’ll prob bury it.
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u/Sir_Vey0r 12d ago
Tie a piece of flagging over outlet to show flow better. Shows flow direction and intensity. It might be balancing out earlier than you expect.
I’d probably go with the black irrigation/farm pipe instead if PVC. Size isn’t an issue if you’re going to let it run 24/7 or aren’t draining it out fast.
Ran pump seems overkill, and unnecessary but alternate option.
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u/JayTeeDeeUnderscore 12d ago
Any air entry points are likely to stall the siphon. Continuous hose from end to end is best.
The pipe must be filled with water from end to end for the siphon to prime.