Pond Boss Forums GENERAL QUESTIONS Muddy water Gypsum cause leak?

Will Gypsum cause my pound to leak? Here is why I ask and it is a long story. My pond was built about 5 years ago and is roughly .5+ acre in size with an average depth of 4ft (max depth 12ft). I used gypsum to clear the water (remove suspended clay) as it filled up and the gypsum worked. Then I stocked my pond. Somewhere in the same time frame I noticed my pond was leaking. I don't know for sure if the pond was leaking before I added the gypsum but I do know for sure that my pond had a leak afterwards. After I noticed the leak I forgot all about clearing the water and have spent the last few years trying to find/fix the leak (.5 inches per day loss and ground wet behind dam). My first attempt to fix the leak was adding 2800lbs of bentonite on the upstream side of the dam (above where the ground was constantly wet) using the sprinkle method. Needless to say, that didn't work. I then spent some more time researching ways to detect leaks. I found a few ways but unfortunately they required a 'real' liner. I had all but given up hope until this year when I ran across a company named Zonge while I was doing some more searching. As it turns out they have a way of locating leaks. I called them and spoke to them about my problem. They said they could locate the leak but most of the time you end up draining the pond to fix it. I was pretty much committed to not draining my pond so I went back to my pond builder who I had been in contact with since it was built. I explained to him of all the cost involved and we decided to give the bentonite another try. So, I put 4000 pounds of bentonite in the suspected leak area. It didn't work. Just as I was about to call Zonge and make arrangements, my pond builder came to me with an offer I couldn't refuse. He agreed to come out and reline the pond at no cost. He said he has built hundreds of ponds and has never had one leak and this wasn't going to be the first. Needless to say I took him up on his offer. A few weeks ago, he constructed a holding pond above mine and we pumped it full of water. Then we drained some more of the main pond down to where he could section it off and build another holding pond. Then we filled the second holding pond with water and moved the fish. The rest of the water was then pumped over the main dam into a ditch. A few days later after the rest of the main pond dried out, I noticed a small stream of water running down the inside of the dam. Everything around it was bone dry. This had to be the leak and it was where I had put the bentonite. My only guess is that the bentonite didn't settle there because the bank was so step. Most if not all of the bentonite looked like it settled in the deepest part of the pond. A couple of more days passed and the old pond was finally relined with clay and lots of it. He said there is no way this dude is going to leak now. So, we broke the dams of the 2 new ponds above and let the water and fish run back in. It was just enough water to cover the deepest part of the pond which is exactly where the pond had leaked down to last year so I knew the fish would survive. Then I got real lucky, the rain came and lots of it. My pond has now filled to within a couple of inches from where it was before we started the repairs a few weeks ago. The down side is that all of the clay has muddied the water. I was about to go get some gypsum and start the whole process over again when I mentioned it to the pond builder and he thought that it may not be a good idea. So, after all this I ask the experts.....will gypsum cause my pond to leak.? I think it would bond with the clay and cause it to sink.....adding more clay to the bottom. I don't think I could handle going through all this again and my wife can not even stand to hear the word 'pond'.

Sounds as if you have a dedicated pond builder,you are fortunate, Gypsum as added to your situation would not of caused the leak.

Yes I do. He is a real good guy. I was thinking that if gypsum would cause a leak there would be alot less people suggesting its use. Everywhere I've read so far says it is a good solution to clearing up water.

I know that if you are trying to get grass to germinate in clay soil you can apply gypsum and it will open up the clay to allow the grass to take root.

That sounds like it is breaking down the clay or softening it....which doesn't sound good.

thanks to all who responded. I think I'll play it safe and use hay. I performed the quart jar vinegar test and the pond water cleared. I went and got 4 bales of fresh alfalfa which should be safe considering I have no vegetation.

For gypsum to "break down" clay, it has to be mixed... tilled in. To test this, take 2 smooth clay balls. Put 1 in a bucket of strong gypsum water, and the other in plain water. Let them sit undisturbed for a week or 2. I don't think you will see any difference in the way the clay reacts.

I hope you saved some of the gupsum in your water, and it's not all wasted.

I think I will try that test and see what happens. I imagine that any of the gypsum that I added years ago got re-compacted after the pond was drained. If I recall, I think I added a couple of 40 pound bags back then.

Well, I won't be trying your suggested test bobad...or atleast I won't anytime soon. Homedepot quit carrying sof'n soil and I can't find it anywhere else local. I'm going to go ahead and go with alum. I ordered some 'lake kleerant' which from what I understand is aluminum sulfate + sodium bicarbonate. I would rather have all my fish die than have a leak again. I'm sure your right, but I will feel more comfortable staying away from gypsum. Plus, I would never get my builder back out here to fix a leak if I do use gypsum.

Bentonite wouldn't help your scenario with a point leak since this sort of clay doesnt have the integrity to bridge an actual hole. It will only work by filling voids between soil particles. It also takes very special care to get the stuff to hold on slopes steeper than three to one.

When clays are exposed to a calcium source (gypsum or lime) the calcium can replace the sodium in the clays and cause shrinkage. This isn't going to happen overnight, however. If you are in an area of hard water, I'd give the pond a few months to see if it clears itself.

By the way, if you used local clays, they are likely already heavily calcified and are not likely to shrink.

Yes, it is all local clay.

I gave up on the gypsum. I ended up using Alum and it worked great.