Pond Boss Forums GENERAL QUESTIONS Help Pond stand pipe blocked

Hey everybody, new to the forum. My wife and I bought a house in Durham North Carolina about nine years ago that sits right next to a 60 year old, 1/3 acre pond. The pond has a drain comprised of a standpipe about 15 feet from the dam in water about 7 feet deep. The standpipe then turns, at an elbow (?) and proceeds approximately 60 feet through the dam to an outlet which extends approximately 3 feet out from the dam. The pipe is made of six inch smooth PVC pipe. The top of the standpipe is protected by a crude screen made up two pieces of rebar. In the past I’ve never had to do anything but paddle out and pull out small sticks, leaves and pine straw (and one turtle shell). This time, however I discovered the drain is blocked underwater. There is a small amount of water continuing to flow through the drain but nothing remotely close to a full flow. With spring rains the water has consistently been 5 to 6 inches above the top of the standpipe therefore draining via the spillway. The spillway has its own issues with the backside slowly collapsing which is its own concern.

I’ve proved with 60 feet of sewer tape from the outlet and 60 feet of PVC pipe from the outlet. In both cases I’ve reached a solid object but have not been able to affect the blockage. I’ve paddled out and, awkwardly, used a metal pole from the top of the stand pipe down and believe I can make out the contours of a large stick caught in the bend. I fashioned a crude hook to try to pull out the blockage from the top to no avail. Admit that the hook was very crude and that perhaps something very sharp could catch the presumed wooden blockage and pull it out. I’ve received suggestions of renting an electric auger but I have hesitated due to concerns of busting the pipe. It’s been suggested that I siphon out enough water to drop below the top of the standpipe then, after some slow drainage, the pipe would be empty of water and it might be easier to clear the blockage. It’s been suggested that I block the outlet to stop the small amount of flow that’s present and then perhaps by removing the flow that the blockage might free self and float up to the top of the standpipe, or at least be easier to remove. It’s been suggested that I drill a hole for a valve/nipple on the side of the outlet pipe that’s visible outside of the dam, then plug the outlet and and apply air pressure to see if that would loosen the blockage. I am stuck and do not know how to proceed. Suggestions would be appreciated!

Questions:
What can I use as a sharp hook to attempt to snag and pull out the blockage by reaching in from the top of the standpipe with a pole?
Does renting an electric auger make sense? How risky is it in damaging and cracking the pipe? Does it include bits that are likely to help me pull out a solid object like a large limb? Or am I just looking at grinding up the blockage?
How would I siphon out the pond? Rent a pump and hoses? Take the 60 feet of PVC pipe I already have and try to create a siphon based purely on water pressure?

Welcome to Pond Boss!!

If you have a friend who's a plumber, they may have a video borescope that you could use to get better eyes on what might be the blockage.

Approx. how long/tall is the vertical part of the stand-pipe, if you know?

Sewer cam is a great idea. Figure out what's stuck, how far down the pipe it is, then figure out how to best remove it.
Large rotary snakes can chew through some pretty tough material.

Great advice above.


If the camera does not indicate an obvious solution, I have seen guys clear out tremendous levels of blockage with a snake using something like a shark-tooth cutter. Those types of tools are flat and smooth against the ID of the pipe, but the cutter blades get a good bite when you rotate the snake. I can't imagine how you could hurt a PVC pipe with that - unless it already had a hole in the pipe.

I also like the idea of blocking/sealing your outlet pipe. You don't even need a perfect seal, you just need the leak rate to be less than the water inflow rate into the pipe. Taking the suction pressure off of the obstruction, or allowing some debris packed onto the obstruction to float back up your standpipe might make it easier to remove the obstruction. Even if it does not work, you have tried a low-cost, low-risk alternative. For seven feet of water pressure, you might even get a seal by wrapping the outlet in some heavy mil plastic drop cloth and using duct tape to cinch it tight.

Good luck on fixing your pipe. Much better to do it now, compared to when the spring rains have raised your water level and it is about to go over the top of your dam!

That is a predicament, and a huge reason that I hate hate putting any kind of elbow or bend in an overflow pipe, but thats neither here nor there now, I would start first by siphoning down the water level with the 60 ft of pipe that you already have that you were sticking up the outside end, that will achieve two things, with all the water pressure pushing against the obstruction from the inside getting it to release or back out will be virtually impossible.

What size pipe is that, go purchase a couple glue on fittings for it, possibly 22.5 degree fittings or 45 degree, then take about 15ft of that pipe, glue a check valve on the deep end, and stick it down the inside of the dam into the water, glue a fitting on the top end that will go flat across the pond dam, then another elbow fitting, then the rest of the pipe down the backside of the dam with a valve on the end of it, should reach way lower then the elevation of the inside piece that went down into the water, thus giving it a siphon ability.

In the middle of the pipe going across your dam, at the highest point, cut the pipe and glue a tee with the third leg sticking straight up, into the upright glue a short section of pipe with a screw on cap.
Now with the outside valve closed and the check valve on the inside end holding the water in the pipe under the pond surface you can remove that cap and fill the whole pipe full of water with a bucket , when it gets completely full, close the lid and go down the backside of the dam to the end of the pipe and open that valve, that should start your siphon. Let it siphon down well below your overflow tube inlet, that will give you a little freeboard before the next rain event, even if it does fill back up with rain before you get your pipe unplugged, getting the siphon going again will be simple.

Then you are ready to tackle and deal with your obstruction, and I am not sure how I would start with that one, I would probably lean toward the idea you had of capping the outlet end and putting an orifice in the cap to blow back up the pipe to blow it back, but rather then compressed air I would be inclined to pump water backwards into the pipe with some kind of pressure pump, that way when you do blow it backward a few inches to get it loose you can keep pumping and float it to the top of the pipe so you can reach and retrieve the stick.

Lastly, if you do succeed in clearing it, look up Agri-drain drop inlet screens to install on top of your pipe to avoid any future problems.

Good Luck! let us know if you have any questions about the jibberish trying to explain how to build your siphon, I think there was a sketch of it on this forum some time in the past, you may be able to use the search function and find it, it will definitely help you visualize it. and it does work like a million bucks, have lowered several ponds with it to do some work on them.

The air idea is pretty good if you do it in a well by putting a small pipe down to the bottom and turn on the air it creates a bubble and pushes all the water out of the casing. You will get completely drenched if you locate the valve close to the well head don't ask me how I know that. If that doesn't work you can get a large lag bolt and weld it to the end of a metal pipe long enough to get to the bend in your standpipe then you can put it down and screw it into the material in the pipe and pull it out

A water jet might also work. You could do this from above or below the obstruction. Would need access to water and a plumber.

Could also try the DIY one if you are mechanically inclined.

DIY Watter Jetting

Welcome to Pond Boss.

Thank you all for the excellent suggestions. I had one new suggestion today I thought was quite ingenious: instead of siphoning water off to lower the pond level below the top of the standpipe (to relieve pressure on the obstruction and improve the odds of removing it/observing it/figuring out next steps), add a temporary extension on the top of the standpipe so it is above the water level and the standpipe can begin to drain itself out. Again this is 6 inch smooth white PVC… I don’t know but assume that I can get a female section to slip on/over it? Need to make it as watertight as possible but possibly not does not need to be entirely watertight as long as more water flows out the far end than seeps in around the joint I’ve created at the inlet. Thoughts?

Google "6" Fernco connector". That was a good thought!

A fernco would work great, but just a regular 6" coupling with a piece of pipe whatever length you need, would shut it off, or even the bell end of a piece of 6" pipe.
Biggest problem with that theory that I can see, you are getting even further from the obstruction, plus the water level would still be elevated to reduce any free-board you might have.
As long as your emergency spillway is fully capable of handling the water with no problems that part wouldn't hurt.

It’s taken me a while, but I want to report back on this. Finally cleared the standpipe and found, not one, but two sticks about 2 inches in diameter and, crucially, about 18 inches long which prevented them from making the turning inside the elbow. One of the key steps, if you recall was lowering the pond level below the top of the standpipe so that the water would drain out and eventually make it easier for us to observe and remove the blockage. I was not anxious to do this. I was speaking to a friend about the need to lower the pond level and he asked why don’t you just extend it 12 inches so it’s above water level? Brilliant! Standby the 6 inch PVC so I found a scrap 12 inch piece and bought a coupling slipped it all all on and even without any glue or tape it was essentially watertight. Problem solved. Clearing the actual blockage was accomplished with a hook on rope dangled from above wall, sitting in a kayak.

Installed a trash guard on the new pipe so you don't have to use the kayak for anything but fishing?

Gratz on the rope and hook!

Great job catching those two sticks!

Hope you checked the relative weights to make sure your pond is producing above average sticks.