Finding/fixing a pond leak

montalvo(z9CA)July 24, 2013

I've had a koi pond leak for over ten years and have expended no end of money and effort in finding and fixing it. It's a small leak but adds about 50% to my water bill.

My pond is gunite/plaster and shares a common wall with my swimming pool. Fortunately, the water level of the pool is about 16" lower than that of the pond, otherwise the chlorine would have leached into my pond, killing my koi.

The common wall section which leaks is only about seven feet long but it's thick and the upper two feet are comprised on mortared granite boulders, not plaster. That, apparently, is the section that's leaking.

if you wanna find a leak in a thin-walled wading pool, you just wait until the water level stops dropping and then you know that the leak is somewhere at the water line. But with my thick walls, the leak could be at or below the water line on the pond-side, since hydraulic pressure could force the water to flow UP.

I've tried draining the pond and coating the granite wall with water sealant and using pool putty (which hardens underwater) to thoroughly coat the grout joints. I even bought some day-glow green leak detector fluid which allows you to trace where water is being sucked through the wall (didn't work because the leak isn't big enough and the lighting is bad).

If the high water bills weren't enough, this leak is also fostering algae growth in my pool, requiring me to clean the filter monthly Any recommendations on a fix, regardless how looney, would be GREATLY appreciated. I'm at my wits end!


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I can only think of lining it with a pond liner, but that will probably not look as nice as what you have. It's hard to find leaks. :(

    Bookmark   September 12, 2013 at 6:59PM
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I've built a pond against sandstone rocks and used glass-fiber reinforced concrete to do it. I believe it's a really great product that you can apply yourself and that might do the trick. I used Quickrete SBC ("surface bonding cement") with only acrylic fortifier (no water) and a little color pigment. Looks great and has held amazingly well. You have to have a drill with a spiral mixer to mix it carefully and then trowel it on as thin as possible and use multiple layers. If I were you, I'd try that out. (The product is sold to build concrete block walls without filling them with concrete, I ordered a bunch at Home Depot, but Osh has some of it in stock typically.) Good luck, sounds like no fun :-(

    Bookmark   July 14, 2014 at 12:48AM
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