Video:
Link to Youtube video

What's the best way to fix this issue? This is a standpipe at a deeper part of the pond, with a rebar covering to keep out the big debris. We've been losing water, and were hearing water running so we sent a camera down to check it out after a big rain. The water level is below the top of the standpipe.

What do you all think?

Best way? Replace it. Any band-aid fix will be temporary.

Ouch!

How old is the standpipe? It doesn't look that old, but it certainly appears to be past its useful service life.

One possible short term fix:

Get some roof patching fabric, a wire wheel for your cordless drill, and roof sealant (that will hold in standing water).

After the water level in the lake drops, pump (or siphon) another foot or two of water down the standpipe. Examine the exterior for any current leaks as well as incipient leaks.

Scratch up the culvert with the wire wheel. (Judgement call on how hard to grind. You want more rust-free bare metal, but DO NOT make any large holes.)

Spread on some sealant and then press a fabric patch in the sealant to cover the hole (or holes with a single patch). Work on more sealant to the specs on the can.

Even if you don't get all of the leaks perfectly sealed, you may be able to get by with the pipe for a while longer. Especially if you pond has a lot of water inflow.

Long term fix?

Can you grout in the next smallest size of culvert and get a good seal to the lateral pipe? If so, you might be able to then just cement the smaller culvert inside the larger leaky culvert.

Bad news.

There is always a chance that the standpipe could fail catastrophically in a big rain event. If so, it could wash out the dam. Probably not dangerous on a 1-acre pond, but hopefully there is not a neighbor's house just behind the dam.

There are experts on the forum that have lots of experience replacing failed drainage pipes. Definitely listen to their advice if you can get them to comment.

Good luck on your project!

I was typing my "band-aid" fix while esshup was posting his pithier response.

He is definitely correct that replacement is the best fix, and appears to be required based on the evidence in the video.

Replacement is most preferred if possible budget and time wise. Just an idea in my head is. Take an over sized pipe and go over the top of it like making it a double thick wall. Could maybe even concrete between them. I'm sure someone smarter than me might say why this wont work. Which is very possible I'm just throwing out an idea.

The reason why I said replacement is that there is no pictures of the horizontal section through the dam. If that has the same holes through it, just patching the vertical section won't do much good.

Rust never sleeps.

Anything other than replacement is just postponing the inevitable.

Being a cheep skate as my wife describes me I always look for the easiest and cheapest way first. Then do it right. But my thoughts would be buy a larger culvert and set on top. Get a trash pump with a 3/4 or 1 inch ridged pipe on it's exit side and use water pressure to dig out the dirt between the two pipes. Hopefully with 4 to 6 inches of space between pipes. When you believe you are deep enough go an extra couple feet. Then put some thing on top, you can use a bobcat or some other heavy equipment to push it down some more to hold the water out for a while. Fill with concrete on the bottom for 10 to 12 inches. Hopefully it would hold water from coming in, then fill with bentonite or if it fills with water, pump water out and fill with more concrete. Your picture shows a lot of holes in your pipe. So my guess would be your pipe was a cheaper product that was used from the start. It will just keep getting more holes.
OR put new pipe on the inside if it would not cut down size to much for your drainage area.
You could plug your drain and put in a syphon type drain, would not have to dig all the way to the bottom of your pond that way. Probably the best choice. But if you would cut it out to the bottom you then could remove the muck on the bottom. See how it gets expensive. You have to love these money pits.

ne hunter, the problem with that is all the $$ you spent doing the "temp" fix is just thrown out the window when it comes time to do the correct fix. If that money was saved, you could have done the correct fix quicker and saved the "temp" fix money.

Metal galvanized pipe like that has a 30,40,50 year lifespan.

Thanks, everyone! I'm glad I logged back in--I thought I'd get emails if there were replies!