If the pond is not shifting that would cause the cracks to widen, a slurry
of bentonite put into the pond and kept mixed with an air stone will find
the leak and plug it in a few days. Once the leak has stopped, then the
pond could be pumped out and fresh water put in to get rid of the muddy
water.

If the pond is shifting causing the cracks to enlarge, or increase in
number, the best solution would be a liner, since virtually all materials
will fail as the cracks enlarge.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html

"robv60" wrote in message
oups.com...
I have a pond made out of concrete that I "inherited" when I bought my
house. It hold about 1750 gallons , that is, when it will hold water at
all. We filled it up and cut our new waterfall on, overnight I lost
nearly 1500 gallons of water to somewhere. We have not been running the
waterfall at all for the time being, just watching the water level. I
did fix some obvious problems with the waterfall plumbing and that will
undoubtedly help. Anyway, the avaerage depth of our pond is about 1.5
feet to the original water line and without the falls running I have
lost about 5 inches of water in about 4 1/2 days. Roughly an inch a
day. There are cracks running in various spots of the bottom of the
pond. Should obviously be a problem, so just to check, I performed the
"milk in a spray bottle" method to see how bad the leaks were. I went
along every major crack on the pond floor/walls squirting milk and none
of the craks seemed to suck the milk out at all. Not even the slightest
bit. The pond was obviously sealed with "somthing", not sure what. Our
front pond is holding water quite well, it seems to be coated with the
same stuff, whatever it is. Funny thing is, the rear pond was holding
water fine until we drained and cleaned it. I guess we washed away
whatever it was that was sealing up possible leaks. Got all the gunk
out and the water has started leaking. I have looked at and priced some
of the UGL Sealant and am wondering if it would be better to just cough
up the dough and try to put a liner in the pond. I figure it would
probably be cheaper than buying all the concrete to patch all the holes
PLUS buying sealant to coat the whole thing and hope that the cracks
dont come back. Thoughts?