This last summer I had issues with my under ground duct work leaking water from where the evaporative cooler connects to the cement duct work. The fix involved fixing a large amount of cement in a vertical application. It’s easy to miss something when patching cement on the inside of a 18 inch hole. I’m not sure if the picture I posted to Flickr shows it very well but I missed one little void, a slot just big enough for a quarter to fit through.
To my great frustration this small slot was enough to flood the underground duct work with water during a rain storms. Once I indentified the problem I had to figure out a way to fill that hole back up with cement.
Regular cement shrinks when it dries. I used hydraulic cement which expands as it dries. To apply it to the hole I mixed a very small amount of it in a ziplock bag with water. I then cut the tip off the bag and and squeezed it into the hole like cake frosting.
It worked great and so far there hasn’t been any more leaking. The real test will come during the summer monsoon season.