The general way to spot a leak is to find the level where it stops leaking. This assumes that it has dropped several inches. Otherwise if it is only a couple inches, it could be capillary action created by a fold in the liner acting as a small tube. A little more info on your pond, liner, and volume/depth would be useful. And the reason you have discounted hose-tubing leaks.

I've been fighting with a leak I've been unable to find for a year. Short of taking all the rocks off the top of the pond, I have been stymied. A couple of years ago a pair of Labs got into it and tore the liner in several places, which we found and repaired, but we must have missed one somewhere. Big enough to drop the level three or so inches a week, you'd think I could find it. We know it isn't a tubing leak, we've checked that thoroughly, and know it isn't in the waterfall. Somewhere in the top 4 inches. Grr. The good news is, the water is so clear you could read the date on a penny on the bottom!

As if that wasn't frustrating, last week something (we think maybe a deer) got into our small 50 gallon woods pond and made a hole in the liner. Now we have to clean it out and find that leak. It never ends.

Sandy

chas045; i replaced the cheap ribbed hose a few years ago with a heavy duty black hose.during the winter the water seemed to stay level with the pump not running.was planning to let the water level drop to where i have to shut the pump down and wait to it stops at the level of the leak.i just hope it's a simple leak to see.pond is 3 and half ft. deep x10ft.

jerome, I have a similar size pond. If the leak is really in the liner, I think you might be able to spot it at the final low water level, perhaps by stretching the liner just above that height around the whole pond. I am still suspecting the pump and piping. I have never had a tear but have lost plenty of water through popped off connections. I would also suggest pump and tubing syphoning depending on your setup, although I don't have external pumps and know nothing about them.

chas045; i have a pump to lower or empty the water. i just hope if it is a leak in the liner it is near the top and can get to it. i'll know within a coulpe of days.i'll just wait till it stops.

I had a leak in my pond, it was at the opening of the pond skimmer, the screws to the flange, that seals the edpm rubber to the skimmer had rusted and it no longer sealed, so there was a gap that allowed the water to leak out.

bob nevin; watching the water leakage stopping, i think i might have a leak near the skimmer. will probably remove the rocks around the skimmer and start from there. thanks

I had a leak in my concrete pond (just built at the time, last fall), I got creative and had a sort of concrete beam in the middle, great for stepping on .. anyway I was losing probably 100 gallons a day .. I let it leak until it stopped, eventually found it under the wall, a couple of little holes, had to wait a week for it to completely stop. Just be patient .. I had to empty my entire pond and re-coated it .. about 2000 gallons ..

I even went snorkeling in my very cold water without success, only when it stopped was I able to see where the holes were, couldn't see anything under water even though the water was clear. Water was freaking cold, so probably could stay down long enough.