Ok ... I have been doing ponds for several years and have never had such a
hard time with a leak. I have made a smaller one and now I have a bigger
one that is two ponds connected by stream (40+ ft in length). My upper pond
(6 - 7' in diameter) was not very deep due to a mistake I made where the
spillway rock was too low (spill way to the connecting stream). As soon as
the water got to the spill way rock, it obviously drained out and went down
the stream which left the upper pond only about 8" deep. A month or so ago,
I picked up that big flat rock (100+ lbs) and filled under it with dirt
(under the liner) so now the spill way rock is about 6" higher up. I had to
take out about half of the rocks in the upper pond to do this and I also had
to redo the seam (there is a seam between the upper pond and the streams).
Now the thing leaks. When I have the pump off, I can see that the upper
pond leaks about 1/4" every couple hours. The good thing is that it gets
to a specific level and stops. Seems easy. That is where the hole is. I
can't find the hole though. To make it difficult, it is about the level of
about an inch or 2 below the spillway rock. So it could possibly be the
seam under the rock. I foamed that area around the rock (with the pond foam
that really expands) in hopes that would seal it.

Couple questions:
1) Does that pond foam really seal it or is it partially seal? I have used
it before to send the water over spill way rocks and that works good. Maybe
there is still water going through \ around the foam and going under the
rock though.
2) any trick on finding a small puncture? I tried putting small dirt in the
water in hopes of seeing if it would "migrate" to where the hole is. Not
enough "current" to do that. I have spent probably an hour looking in a
small area right along the water line where the water stops going down and
just can't find it.
3) I searched the whole area where I moved rocks last time and looked under
the liner and it wasn't any wetter than if I felt in the dirt in the lawn.
Does the water "run down" the liner until it is directly under the pond
instead of being absorbed in the dirt right next to the hole?

I am baffled. My next thing I am going to try is to basically redo the
spill way rock again. Redo the seam, put the rock back and refoam around
it.

Thanks
Darren