I have a pond with a vertical standpipe spillway. It's constructed with a concrete standpipe about a 4' wide at the top and at the bottom has two connected horizontal (plastic I think) pipes leading to a stream. (Water flows in from the top)The problem is that I have some leaking where the bottoms pipes connect the standpipe. I've slapped on some hydraulic cement I bought at Home Depot and its stopped the smaller leaks. I still have one major leak that is small but the water pressure is too much for the HD cement. I've heard of a commercial cement with "plug" in its name and maybe its better - but I don't know the exact name? Or any advise from this forum would be helpful.
Thanks,
Bruce

BruceO WATERPLUG made by ChemRex Shakopee MN.(800-433-9517 comes in 1Gallon paint can =10 lbs might call them to see who sells it close to you. Hope this helps PO

My recommendation would be to pump the water down to where you're below the spillway and get down there to patch it as well as possible. It's going to be very difficult to patch with water still flowing, especially if the leak is relatively large.

You can rent pumps from most rental places, or find one on the cheap on craigslist like I did.

Go to a contractor supply house, not a big box store and call/ask for Sika Plug made by the Sikaflex Corporation. We used it to seal a floating concrete 4-lane highway where a diver had to go down and apply it on the outside of the concrete. We were inside the flotation compartments injecting 2-part epoxy into the cracks to seal it. The Sika Plug stopped the epoxy from oozing out into the ocean. IIRC we had the capability to pump at over 8,000 psi (air over hydraulic).

Sika Plug PDF