I just noticed it today, but it's probably been this easy for years.

I've had this pond for just under a year (it's 30 years old). I noticed today that water was trickling from the overflow into the creek behind it, and I know the water level is below the overflow port.

I jumped on top of the concrete tower and could clearly see water leaking into the bottom corner of the concrete structure. I estimate that it's easily flowing at 1 gallon per hour.





They're a spring fed pond about a mile up the road that feeds the creek behind the pond. I guess it's possible there's a spring feeding my pond, but I don't think that's the case. Aside from runoff the only other water the pond gets is outflow from my openloop geothermal.

Can I fix this? Also, can I fix this without draining the pond?

Thanks for any advice.

Here's what I'm thinking:

https://www.sakrete.com/products/leak-stopper-hydraulic-cement

Try flex-seal it works great in the commercial. Really just kidding but who knows might work great. There are materials that get hard when it gets wet. Theres a product called Conseal we use at work. We use it under some tanks it makes a seal between concrete n steel. Some of it expands so much tht it will bust the concrete. I would say you would want to lower the level to just under the leak. Theres no reason to drain it all for sure. I'm no expert just giving my opinion. Take it for what it cost (free). I'm sure there will be others chime in with other materials. I would do alot research before doing it. I wouldn't be scared of giving it a try. Always be careful water is very powerful.

Now that I've been inside of it and attempted a fix, I can be more specific about what's going on.



The tower is made up of two preformed concrete boxes with additional concrete walls poured all around it to seal them together.



It's leaking from almost the entire perimeter of where the two preformed boxes are stacked together. It's also leaking where the bottom outlet pipe exits the drain tower. In other words, it's a mess.





I pressure washed the inside, as best as I could, and I spent a whole day trying to patch the leaks with hydraulic cement. I'd plug it in one place and more would just come out in another. I eventually got it to where it's just trickling a little.

Even though I have mostly stopped the leak. I know I've wasted my time. There's no way this fix will last very long. The hydraulic cement is mostly plastered over top, it's not addressing the actual leak. If it lasts the summer, It guarantee it wont last a freeze.

Bentonite around the outside?

I hadn't thought of that. Something I'll have to read up on for sure.

The good quality hydraulic cement will fix it permanent if done correctly, I have seen it used to completely seal a garden hose size flow of water in a matter of minutes, I get it from my local pipe supply place in a 5 gal bucket, the blue lid bucket will do the same thing but take a little longer to set up, the red lid stuff, which is what you need, will set up quick, you might chip a little concrete back to make sure you have good clean concrete for it to bond to, and also a better gripping surface,,, will not bond to a grimey surface. and when you have a stream of water coming thru, apply it to the flow dry, and hold it in place with your hand or trowel, it will literally get wet, bond and seal in a matter of a couple minutes.

I had a very similar situation - a concrete box that serves as a duck blind which sits mostly submerged. Poured in 1955 we have killed a lot of ducks out of it. Anyway it developed a crack and leaked. About 18" of water inside per day had to be bailed out to sit in it.

I waited until the outside water level was about gone then brushed the area hard with a wire brush, chipped a bit along the crack to widen it, and cleaned it with muratic acid. Then applied hydraulic cement. Its held well for three years now, including ice inside and out.

I would have used a pressure washer if accessible.

Think of it just the same as you would a basement leak.