Pond Boss Forums GENERAL QUESTIONS Help Stand Pipe Clogged?

1/5 acre pond. Just moved in last summer, so don't know much of pond's history. 6" pvc vertical pipe meets an elbow and then goes horizontal through the dam.
In periods of heavy rainfall water level can get a foot above the top of the stand pipe at which time it flows through a secondary emergency horizontal pipe that goes through the dam.
If the stand pipe is full I would assume that the outflow pipe on the back side of the dam would be full. In fact, the outflow pipe is only pouring out at about 1/4 the diameter of the pipe.
I am further assuming that the pipe is partially blocked. I snaked the stand pipe and could not sense any blockage. The horizontal section is approx 75 feet and I don't have anything long enough to send up there. Does my assumption that the outflow pipe should be full if the vertical pipe is full make sense?
Any suggestions would be appreciated.

Troutrus I would rent a trash pump and try to pump water backwards through the pipe. You may be able to push debris back out the top of the standing pipe.

I've successfully unclogged a horizontal section by gluing sections of pvc pipe together and pushing up the pipe from the downstream side. My clog was about 120' up the pipe. 12 sections of pvc pipe.

Good options. Rjackson, what size pvc did you use?

3/4"

Whatever you do don't go under water to the intake and allow an arm or leg to potentially get sucked in if you suddenly get the flow going. I know someone that almost drowned doing something like that. A lot of suction force in a 6 inch pipe when it gets flowing.

You may actually not have a clog. If your horizontal and vertical pipes are the same size you will never get it to flow full. NRCS has a table with the correct ratios (USDA Pond Design, Page 38, Tables 12/13). The other piece is the actual elbow. I cannot find it at the moment but I recall reading that extending the vertical pipe at least 1 foot below the horizontal pipe will also increase the ability of the water to move through the horizontal pipe.

If you have seen the pipe flow full prior to the clog then ignore everything I said b/c I don't actually know what I am talking about!

Definitely second what Cecil said, yesterday a guy a few miles from me was found floating in his pond. Thirty minutes prior he told his wife he was going to unclog the outlet. Scary stuff. Man found in pond

If you put a 22 degree elbow, pointed upward on the main drain outlet (to prevent air entering from the outlet and flattening/slowing flow, it can create a siphon when the inlet is completely covered and no air enters. once air enters the inlet, the siphon will break, but until then, flow will be massive through the main drain in siphon mode.

What Rainman says is what you want. Its a upside down P trap that will let your pipe run full until the water level is down to a whirlpool will start and suck air breaking the seal.

These should not clog when the flow starts shes on.

you need a larger vertical pipe connecting to the horizontal pipe. it is called a riser. like ben said, there is a ratio. also needs a cross in there to break the vortex. my old pond had a 12" pipe vertical and horizontal. it never carried but about a 1/3 pipe full at discharge. my new pond has a 10" horizontal and a 12" vertical. it carries a full pipe during heavy rains.

Thank you everyone for your input. Anyone have a diagram or photo of the setup that Rainman is referring to?

Troutus, all you need is an elbow with enough angle on it that water is always in your outflow pipe.

Yours is a traditional stand pipe it sounds like, not a "true" siphon setup, but the elbow on the outlet of this drawing from Pond Dam Piping is what you want to add.

You can also change your stand pipe to a bottom draw system by merely slipping a larger and slightly longer pipe over the your current stand pipe...that will stop top water from being pulled in and draw it up from the bottom instead.

Thanks for your reply Rainman, but mine looks more like this and I can't picture where this elbow would be placed.

troutus, I sent you a PM.

Update. First, After inspection we found that the vertical stand pipe is 8" and the horizontal drain is 6".
We built an 80 foot long ramrod with 3/4" pvc as suggested by Rjackson. We worked the long ramrod in the horizontal and a ten foot piece in the standpipe working from a kayak. By adding water, we were able to free up the clog. Amazing how much silt, leaves,and small twigs flushed out of that pipe. I can still see a couple small pieces of tree branch at the bottom of the vertical pipe, but all the soft material that had accumulated is gone for now. Next heavy rain, we will know for sure.
Now we need to figure out the best way to build a trash rack to go over that 8" stand pipe.
Thanks for all your input.

Bob

that stick or tree branch is probably what is catching the small stuff as it passes through....

Drop a heavy treble hook into the stand pipe and "fish" out all longer branches caught in the TEE or they'll just trap smaller debris again.