Pond Boss Forums INTRO Questions & Observations Siphon system understanding and troubleshooting

Good eve,
New to the pond scene.....bought a distressed property last year that included a deep (16+') one acre pond with a siphon drain system. My first experience was noticing the level drop after a large rain because of leafy much blocking the siphon tube. Second time it was a water turtle that blocked it. I could hear the air whistling from 100 feet away......poor guy was totally dried out by the time I got there. Learnings - the system worked.

Helene wreaked havoc on my pond and general area so much; not surprisingly my pond overflowed the dam after 9+ inches of rain. Last week, I noticed it ran over again after 3" in 3 hours. Not a total surprise, but I see little evidence the system is working well, and it may just be my understanding of the system. Here is where you all can help......

The first pic is of the siphon tube. At this point, the end is still fully submerged. Note I now have a screen over the end to keep the turtles out. Right next to the siphon tube is the drain tube; not sure but looks like 8". It runs up through the dam and down the embankment to the receiving stream. I see no indication of any access to either of these pipes anywhere between the edge of the pond and the receiving stream.

The second pic is of the drain releasing water into the receiving stream. Note there is a small amount of water coming out; I estimate 1/2 deep stream of water. Am I wrong in assuming the flow should be full-on as long as the end of the siphon tube is fully submerged? I am wondering if the entry end of the 8" drain pipe has clogged on the bottom of the pond? Is there a way to tell? To clean? I have poked and prodded the top of the dam thinking there may be an access valve at the highest point to clean out the drain pipe and to use to fill the pipe to initiate a draining?

The 3rd pic is of a "mystery" box I found about 10' from the end of the drain pipe, and only after finally getting the dam clear of years of growth.......trees up to 10" diameter......yikes. My dog actually found the metal lid under years of leaves. Lo and behold, there is plumbing inside. Not for sure, but I think it is all one line. The open pipe with a "flag" welded on appears to be a valve. Quite rusty, so a little afraid to try to turn. Down from that (an inch away) is a boiler drain. Again, appears to be closed but I am a bit hesitant to try to turn. Finally, 6" down from that is a spigot. This will turn, and is presently closed. I have no idea what any of this is. Can someone help me understand what all of this is, and how to operate it to make it do whatever its intended purpose is? I sort of wondered if this valve closes the main drain pipe to make it easier to fill the pipe in order to start a siphon?

I have what is to me a critical situation here. Every overflow is causing serious erosion. I need to make sure everything is working as designed.

thank you in advance for the advice! David in SC

Yes, water going over the dam is probably the worst thing possible for the well-being of a pond! Keep working to fix your existing siphon system!

I don't know if your siphon system was large enough to protect your pond from overflowing during Helene. However, it should have been designed to pass a 3" rain without the dam being topped! If it is an older pond, and the dam did not previously get washed out by multiple overtoppings, then I think your siphon system has been partially disabled fairly recently.

One emergency solution would be to buy some 6" flexible corrugated pipe at your local big box store. (It is cheapest at the Menard's near me.) You can create a siphon by capping the discharge with a painter's plastic drop cloth and duct tape. Use a water source to fill the inlet. When it is full, carefully place it in the pond, and have a buddy immediately slash the discharge end plastic with a knife. It should start a roaring siphon. You can either do that before forecast rains and draw down your pond a little. Or if you get quick about it, you can do it when your pond level is rising towards the top of your dam.

Good luck on saving your pond!

Excellent advice FishinRod! Thank you; I will get on your recommendations and post back.

Crazy thought. If I build a plug for the exit, is there any chance I can do anything by inserting my leaf blower in the end? If nothing else, maybe it tells me how far out in the pond my inlet is?

Another crazy one......I have a GoPro and a waterproof light. Thinking about rigging them both to a long cane pole and livestreaming to my phone as I follow the inlet pipe into the deep?

I am the most avid DIY'er, and not rich. I love to try to figure stuff out before I call in for help.

You all are great, and I appreciate it!
David in SC

Well, I tried the leaf blower into the discharge. Air blew a geyser out of the siphon tube, but not a bubble in the middle of the pond. Looking back, I suppose I should have had my wife get in the pond and plug the siphon pipe, hehe. As I see it, this experiment only stronger supports that the discharge inlet is clogged. Thoughts?

I also uncovered the siphon tube enough to find a 90 elbow heading down to where the discharge pipe is..........But, it has a rubber coupling with hose clamps just before the 90 degree. The rubber does not show visible damage that would break the siphon, but I did not dig. I suspect I could de-couple this and use this to fill the discharge pipe to create a siphon. Hmm, wondering if trying to siphon would be a wise move, or would it possibly compact even more what could be clogging the pipe?

I do have a gas irrigation pump I intend to use to try a few more things, and will likely try to pump down the pond level if rain hits the forecast.

All advice is much appreciated. Thank you,
David in SC

And one more thing...........no pic, but I also have a steel valve assembly sticking out about 3' above the water level about where I suspect the deepest point would be. It has the gate valve assembly on it. Just curious; why would this pond also have this? If I understand correctly, wouldnt that mean I have another drain pipe and/or method to drain the pond in addition to siphoning? I have only kayaked out there one time and noted this assembly to be very wobbly. But, I suppose if it is connected to a pipe maybe 15-20' below, that may be normal.

Just a little more loss of sleep while I try to figure out this pond. Beautiful pond, but clearly neglected for many years. Hope to get my aeration system going soon.

Thanks again,
David in SC

Well, have done about all I know to do. Wife and I capped the drain using a coffee can wrapped with rubber belting. I then drove it in and drove rebar in the creekbed to leverage against the plug to create a good seal. She then ran 2 hoses off our Harbor Freight 2" water pump into the 2" siphon vent pipe to fill the 6" drain (previously stated 8", but is actually 6"). At the point I could not hold the plug in any longer, she killed the pump, removed the hoses, and closed the gate on the vent pipe; I just happened to have a 2" PVC gate valve that I put on the stub in place of the 45 that goes into the pond to control the water level. This should have created a perfect seal. I then removed my home-made coffee can plug and wow, did the water come. But, it only came for about a minute, and then slowed back to the trickle that has been all week. Frustrating. We did this twice with the same results.

I also tried a gopro all over where the drain pipe opening is thought to be, but could not locate it. Had it strapped to a 16' can pole, so keeping it in the water was a challenge.

Tried grappling the area and pulled up some muck, but nothing that concerns me.

Wondering if I should try to hook the full 2" pump to the siphon vent tube instead of the 2 garden hoses? Makes me a little nervous. Dont want to do more harm than good.

Tried hiring a diver, but he would not dive it due to the risk of a siphon system. Fully respect that, even though this one is not siphoning.

Any other advice? If I had a 300' roto rooter, i could try to go up from the creek through the dam and into the pond. But I dont have one.

Rain on the way, so running 2" WP to try to create some needed capacity to prevent another overflow.

Any further thoughts?


Thanks you,
David in SC

moukie,

The situation you describe is consistent with the siphon breaking suction. This would be caused by air entering the siphon system and breaking the suction. Most installations are designed with a suction break that will stop the siphoning when the water level in the pond reaches a desired lowest level. In a design like this, there is a riser that will introduce air into the siphon. It is always open and has just the right amount of restriction to air flow to allow the siphon to charge automatically when the pond level rises to its highest designed level. This should be below the emergency overflow of the dam. Once charged the siphon should rapidly ramp up to a maximum discharge. While this is going on ... there is air being sucked into the siphon but it should be restricted enough that it does not break suction and stop the siphon. This design's goal is to break suction before your pond is emptied past a certain level. If you have this design, it would have a conduit open to the air and it could have a valve on it to adjust where it stops the siphon (lowest desired pond level). It must be restrictive to allow the siphon to get started. IOWs, it needs to restrictive enough to start before water goes over the emergency spillway. It must not be so restrictive as to lower your pond to an undesired lowest level.

First, verify you have a suction breaker conduit and that your installation is designed to operate as described above. If so, AND if the suction breaker conduit has a valve on it, AND that valve has been closed all this time, then you are probably losing suction either between the valve and the siphon or somewhere along the siphon itself.

Thanks jpsdad!
Your explanation sounds exactly like my system. I have a 6" pipe that runs from somewhere in the middle of the 16' deep pond through the dam, and approximately 25 foot drop into a receiving creek. At the edge of the pond just above the 6" pipe is a 2" pipe that 45's down to the water. I would call this the siphon vent pipe? This pipe comes from the edge of the pond into a 90 degree fitting and appears to go into the 6" pipe; I have not dug deep enough to verify, but that makes sense. Just before the 2" siphon vent pipe reaches the 90 degree to turn down and go into the main 6" pipe, there is a rubber boot connector that enables one to de-couple the pipe. I sort of suspect this was put there to enable you to manually fill with water and create a siphon? The rubber connector is in good shape.
By reading your reply, it appears everything should work, and I have heard it work before. Last Spring, I noticed my pond level rapidly dropping after a heavy rain. I could hear a whistling 100 yards away. Turns out a turtle had stuck himself in the 2" siphon vent pipe, preventing enough air to enter and break the siphon. Once I removed the poor dehydrated critter, the pipe quickly released the siphon and the water stopped flowing. By this time, the pond level had already dropped below the end of the siphon vent tube, so it took a while for it to fill back up to full pool.

We have had 2 major rains in the past 7 months and both have caused the pond to overflow the bypass overflow dam. Erosion is starting to happen, and there is not an easy way to get equipment or fill in to make corrections so I want to prevent more. This had me looking at if the system is still working properly, and it does not appear to be. I have tried for 2 days to create a siphon and I cant make it happen. Suspect I have a clogged pipe in the botttom of the pond?

How about the roto rooter man with a camera; any idea how far they can push a camera up a pipe while standing in a creekbed?

Thanks to all!
David in SC

David,

So the first question I would ask right now is where is the pond level in this moment? If it is overflowing the spillway ... then something is definitely wrong with the siphon. If it is overflowing the spillway and the water coming out the exit end of the siphon is sluggish, then I think the first place to look would be the inlet of the siphon as you suggested.

You may not need to do anything other than that to correct the situation. I would just mention that a 2" suction break seems a little large for a 6 " siphon. I would rather expect to see 1" ... possible 1.5". It does however depend on the head from apex to exit how much you need to restrict the suction break. I also expect the break to be at or near the apex of siphon (rather than under water). If your pond is flowing over the emergency spillway, the siphon should be roaring and if it is not ... there is either an obstruction or too much air breaking the suction. If your pond level is lower, you may not be able to charge the siphon sufficiently and will need more water flowing into the pond to get it to work. If the pond level is consistent with the apex of the siphon, then your siphon is just working to handle over-flow and a suitable suction will not develop because the flow is too low.

Rather than wait for rain, if you have a fair amount of flow that could fill the pond in a few days AND if there is no rain expected in the watershed for the same time period, you could block the exit of the siphon by installing a full opening valve to allow the pond to fill completely. When you open the valve, the siphon should go right to working. Personally, if I were to add a valve for a test like that I would take off after the suction was broken and my test complete. Anyways, once you have the siphon charged it is just a matter of fine tuning the suction break to shut off at the desired freeboard. The more restrictive the suction break (smaller diameter is more restrictive) the lower the level your pond will go before the suction of the siphon is broken. I really don't like a valve on a suction break (You never know who may come along and close it or what not). But if you could put a collar on it, you could test different sized reducers in it to see which stops the suction at the most desired freeboard.

One last thing, there is a limit to how much water can pass through a siphon. It is possible it was much too small for those heavy rain events. IOWs the siphon may have been passing all it was physically capable of and the flow into the pond just vastly exceeded the siphon's design. You many need to shore up your emergency spillway. There are concrete pyramid shaped thingies (sorry don't know what the actual name of those things are) that can be deployed. Not sure but they may have a spike that is driven in. I've seen them on spillways and even the dams of small lake-like ponds. Anyways the look like a pyramid with the top cut off and they are arranged in rows and work to deter erosion.

Thanks jpsdad!

You are absolutely correct in that there may not be anything wrong; may just be that I dont know how to create the siphon. Here is how I tried to create a siphon:
1) Remove the extension of the siphon break that dips into the pond to maintain desired water level
2) Install a very tight fitting gate valve on the line
3) Run 2 garden hose feeds into the gate valve opening
4) Plug outlet that runs into creek
5) Run gas water pump about 15 minutes to fill siphon pipe at least from creek to top of dam (until my home made plug is about to launch at me)
6) Wife shuts off pump and removes garden hoses and closes gate valve
7) I remove plug and stand back while water drains like a water main break

We did this 2-3 times and I really believe this should create the siphon. Instead it drains, surges a few times, and then goes dry.

I do have fittings to forget the 2 garden hose approach and hook the 2" water pump hose direct to the siphon break tube. This will fill the downside column in a rush, and SHOULD send some back through the entry and could POSSIBLY push a potential blockage out the entry......maybe? But, I am afraid I may not be able to hold my home made plug in place, and more importantly, I dont want to risk damaging any parts of the system. Though it is not high pressure, that 2" pump moves a ton of water fast!

One critical piece I have failed to mention is that there is always about 1/4" deep flow of water coming through pipe. Not sure I understand this, unless the height of the 6" pipe going through the dam is the same height as the current water level? If this is the case, this would mean I would never be able to raise the level?

Water is not currently overflowing, but is rather about 1" higher than the end of the siphon break pipe. That is what caused me to suspect the system is not working properly; though I know it has as recent as last Summer. Pond is about 30 years old, and was obviously very neglected by PO. I have a real challenge saving this, and the property, and will have a treasure if I can do it.

Thank you kindly for your assistance. I am heading down at daybreak to put up a silt fence. If it does overflow, at least I can try to divert it to erode a different part of the property.

David in rainy SC

If the water level in your pond is about the same level as the apex of the siphon, then I think what is happening is that it just flows through the siphon at the same rate water is entering your pond. I think that is what is going on and that this is why it is not easy to get the siphon charged. The siphon should only charge when the water level is too high (but below the emergency spillway).

To charge it at this level and maintain the suction you may have to prevent the suction break from killing your suction. Normally the pond level is higher when the siphon charges. That higher water level will provide substantially more flow to the siphon than your current water level can. There is balance between the amount of water flow and the amount of air coming in through the suction break. Too much air coming in through the suction break could be making it difficult for you to charge the siphon at this pond level. Looking through your steps, it doesn't appear that you have tried preventing air from entering the siphon break. You may try closing it off on its end and then try all the steps you mentioned again. If there isn't an obstruction at the entrance of the siphon, then it should go to roaring (assuming suction isn't broken from the exit side due to lack of sufficient flow).

Word of caution, if this worked, the siphon would continue working until the pond is emptied to a point where air sucked into inlet of siphon breaks the suction ... however deep that may be ... unless you can easily open the suction break again to kill the suction. You might first verify that it is the suction break that is killing suction. Trying all the steps again, have an assistant observe what happens on the pond side at the suction break when you remove the plug. By your account, the open end of the suction break is below the surface of water (something I missed before). So, if it is breaking suction, a whirlpool will develop, and air will enter into the siphon killing the suction. Although this wouldn't verify the inlet is not obstructed, at least you would know if the suction break has been a problem for charging the siphon at the pond's current level. If the suction break didn't form a whirlpool, this would not necessarily mean your inlet is obstructed. Suction can break on the outlet side as well if the flow of water is not sufficient. At your pond's current level, it may not be possible to manual start the siphon due to the inability to initiate a sufficient flow of water.

It is always best to confirm proper working condition at the siphon's limits of pond levels. The pond level that initiates suction and the pond level where suction is broken. That's why I recommended allowing the pond to reach a level where the siphon should activate. Just want you to be safe without having unwelcome surprises. I'll close with this. The current status as you described it, is just what I would expect from a siphon that is working. It should let just enough flow through to balance the flow coming into the pond. It could be difficult to manually charge at this level. This of course doesn't mean that there is not something wrong. Not much help, I know, but you seem to have a good handle on how the siphon works and will be able to determine whether it is working or needs corrective action.

Morning All. Quick question moukie, when the pond is overflowing the spillway, or at least higher than the apex of the 6" syphon pipe, does the flow from the syphon pipe increase? Seems to me that it should be more than pictured whether it creates a syphon or not. If it's not significantly more than pictured, then there's a block in the main pipe somewhere.

Thanks rjackson, for the input. I have to do some digging to give conclusive answers, and I plan to do that soon.

I am beginning to wonder if I really even have an issue. We had about 1" of rain today, so I went to the pond. Understand that we had the siphon vent pipe off and out of the water all weekend, so no siphon should have been present prior to today's rain. The level was clearly up, and about 1" of the siphon vent pipe was underwater. I did have flow(increased) at the downside creek. Clearly not full blast, but about 3/4" deep in the 6" pipe. Only digging up the siphon pipe where it goes through the top of the dam will tell me whether my flow is due to gravity or siphon. My previous understanding was that a siphon system that never loses suction will run wide-open until the level of the pond drops to where the vent tube sucks air? Now, I am hearing a siphon system will only release water at the level it is entering the pond.......not sure how this thing works, but for whatever reasons, my Wife and I were not able to create a siphon so I assumed we had a blockage.
Weather reports for the rain last week confirm we got 4.7" in 3 hours. Maybe that was just too much for the pond to handle.

I dug up the siphon vent tube tonight; hoping to find it to be a threaded coupling so I could remove and send a sewer camera toward the pond. No luck.....it is a glued fitting coming out of a 4x2 flange. Tells me their is also a 6>4" fitting in there too.

The work continues...........

Thank you,
David

Most of the time ... the siphon is not siphoning. It just acts like a culvert. This is because most of the time there isn't enough water flowing into the pond to fully cover the siphon. When the water level rises above the highest point of the siphon (the highest elevation INSIDE the siphon) things begin to change. There is pressure that can fill the siphon fully and purge the air. At some pond level above the apex of the siphon ... a point of no return will take place ... and the siphon will purge the air (or at least most of it) and will develop a suction on the pond side that will lift water. Once activated by high water... it will roar ... provided your inlet is not obstructed.

Great explanation! I think for now, I will sit back and wait for that moment. When it happens, I hope to report all is well.

Thank you all for the generous advice!
David in rainy SC

In the meantime, put something over the air inlet that will prevent a whirlpool breaking the suction early and turtles from plugging it. Maybe an end cap with a bunch of holes drilled in it, or stiff metal rods pipe clamped to the end to point up past the opening.

If something winds up preventing the suction break, you may be able to later walk down to the inlet at the bottom and see what is going on. Not that you would want to.

Good morning! Update on where we are..........Had a local pond builder, with lots of nice ponds to his credit, come do a walk-around. He was emphatic about how nice and well built our pond is, and states to not get excited but rather just observe for a while. See if the siphon system is working before assuming it is clogged. He says this because:
1. The dam is about 4" higher than the water level, and is in no danger of eroding away. He did say I might want to increase height of the backup spillway about a foot to make sure the siphon gets activated before it can run over
2. I have put in place a silt fence to prevent erosion in the current place. Also put in a 6" pipe should water get by, and even stapled it to the bare dirt. Beyond that, the water will travel down a fairly level grass roadbed where it should level out and make a gentler path to the creek below. Pipe is 100', and runs all the way to the creek.
3) Pond appears very healthy and capable of making it through an occasional overflow with measures I have in place.

He believes the old rusty gate valve was likely an original drain system that may be lead to the 4" pipe in the valve box in first set of pics. Likely capped off and turned into a hose bib, along with a later addition of the siphon drain system. No apparent cleanout access port on top of the dam, which is a bummer. But, he says I can hook my 2" water pump to the siphon vent port, while capping the outfall, to try to blow out any potential clog if I choose to. He says there is no potential to damage any piping.

Overall, a very health report, from a very nice local construction expert.

Thank you all!
David in SC

Came across this forum yesterday while researching a siphon problem we are having here. Just read through most of this thread on you problems. Hopefully I can help a fellow South Carolinian. Not sure I follow all that has been said, and I didn't read through in great detail, but I have been maintaining a siphon system here for 18 years. I designed it in consultation with some local engineers, oversaw the installation and have been maintaining it ever since. We have a 6.5-acre shared pond with about 12 feet of head. One 12" siphon and two 6" siphons, with 2" piping for the control vent (that induces and breaks the siphon) and the vent at the highest point to break the siphon as needed. I do the lion's share of the maintenance as the siphons are on my property.

As far as basic components, a picture is worth a thousand words, and I assume you have something like this.

https://www.tractorbynet.com/forums/attachments/pondsiphonimage-jpg.466506/

One thing I learned early on, is that the 45 degree ell at the outflow is essential to form a trap so air doesn't enter the pipe from the outfall and break the siphon. We didn't install that at first, and the siphon wouldn't kick in until the outflow to the creek was fully submerged by the rising water during a rainfall. When you speak of charging the pipes and a gush of water issuing forth but then stopping, and sometimes the siphons working but other times not (if I read correctly), that would be consistent with not having that ell at the outflow. Do you have one?

Also, rather than fashioning a cap for the outfall to use when filling the pipe with water, we installed ball valves. Work great, but they do get persnickety with time. Can't get one for the 12" pipe, and we have to clamp a (leaky) cap on the end whenever we need to charge it to get a siphon going to clear a plug over the intake. You mentioned a submerged valve, and that may be to valve off the intake piping below water level so you can fill the pipe without waiting for the pond level to rise enough to fill the run of siphon pipe through the dam. Just a guess, as I have pondered installing such a valve myself.

Beavers have been our biggest problem here, by far. They can plug our intakes beneath 12 feet of water in short order, and every time we manage to unplug them they move less water, as some detritus remains around the intake. We are at the point we are pondering mods to put our intakes in more shallow water just so we can clean them fully when necessary.

Anyway, hope there is some useful information for you here.

Steve

Thanks Steve!
Your drawing is almost spot-on for my system; at least the exposed parts. I do have a 45 on the end. I first thought this was to minimize creek bed erosion, and later learned it is there to assist with the siphon system.

As far as plugging the hole, I am still in the homemade approach. The plugs and caps I can buy on Amazon or at Lowes fit a piece of 6" pipe, but do not fit a 45 coupling for a 6" pipe. What I really need is about a 3" piece of pipe to solvent weld into the 45, so I have a true 6" pipe to adapt a ball valve to. I just have not found a source for a 3" long piece yet, haha.

I am still not sure if my drain inlet is clogged, and I expect I may not find out until the next big frog-choker. I will be watching. I was wondering how deep beavers will plug a hole. I have no active signs, but there is plenty of muck and brush in my pond.

Thank you for your help!
David in Greenwood, SC