Here's a picture of the cleaned out pond now. The hole at the deep end is where i broke the "crust" of cement that had been laid over two feet of gravel used to fill the former koi pond. That is what I intend to repair with the concrete patch. When I said "stucco" above, I'm not sure I was accurate. I don't actually know what was applied over the concrete and stone. But you can see in the picture that I am now dealing with several surface types - stone, concrete, and remnants of the former sealant or stucco. Drylock on all of it??

There are many things you can do...but there is a fundamental issue. Concrete ponds/pools rely on thick concrete and steel enforcement. As the structure moves (to some degree) the strength of the structure keeps it from cracking.

These thinner structures crack. You coat it and it's water tight for a day, a week, a month, a year, but cracks come back. Then you repeat, and repeat and at some point give up and fill in the pond.

With the amount of work you've already done you could have just pulled that out completely and laid a liner. If you still want the look of concrete you can put a thin layer over the liner. The cost of the Drylock you'll need over the next say 5 years will be more than the cost of a EPDM liner. The cost of Drylock for just this one application will cost about the same as PVC liner and the liner will last 10 times longer.

The problem isn't in sealing this, the problem is you can't seal concrete that moves.

DON'T Dryloc it! I did and it caused more trouble in the end. Dryloc is great for basements but it isn't made to actually hold water.

It is quite possible to effectively seal concrete and it's a lot easier to deal with than a stiff liner. There are several products (Pond Armor, Thoroseal, etc) but the one I have actual experience with is Permaflex by Sanitred.

Here is a before and after pic of my 7 year old pond.

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This shows an area (and a free standing rock) that was properly treated 4 years ago. Under the rock overhang you can see an area where the Permaflex did not penetrate because I had applied Dryloc first.

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I would advise cleaning and patching the cracks with hydraulic cement. Be sure to chisel the crack out in an inverted "v" to get the maximum amount of cement in. Then power wash everything (I would not advise bleach). You want to get down as close as you can to the original material. I used a biodegradable paint remover called "off the wall".

For my cracks and also the area where the cement met bare rock, I used a liquid rubber that has amazing tensile strength. Even after 4 years none of the areas with liquid rubber cracked or broke. Then 2 coatings of Permaflex over everything.

My pond is about 3500 gallons (irregular so it's hard to tell) and 19' by 10'. The entire cost of three gallons of Permaflex, liquid rubber and paint thinner was under $500. If I had done it right the first time 4 years ago I doubt I would have had any problems since all of the original installation is still perfect

Here is a link that might be useful: My Pond (old site)

Getting a "V" in 1/2" or whatever thick stucco...not really possible. The vibration trying to will cause lots of other cracks.

And when the stucco cracks after adding these expensive products...just repeat the process.

Now I am bereft! I hired a mason to repair the hole with hydraulic cement, brush off all the peeling stucco or old paint and mold, and coat with two layers of DryLock (I had already bought it). We filled the pond, and it drained overnight! It was not leakage from the waterfall because we turned that off. Now what?! I can't do the liner option because there's no way to affix it. I now have the drylock to contend with. What do I do??

Of course there are ways to attach a liner.

Can someone please explain how I can attach a liner to my stone and concrete pond? It is straight-sided with large rocks cemented started at approximately the water line. Thank you!

It depends on exactly what's where...and there are several methods.

All of the following are done a bit above the waterline, but careful that the attaching method be level so it looks better if it's to be visible. I use a water level for this.

For flat areas I drill a hole into/thru the concrete and then using masonry screws I screw a board to the concrete. For even an 8' length 2 screws are plenty.

The board is parallel with the waterline. I nail the liner to the board using 1/2" roofing nails. The nails have to be above the waterline. I prefer to nail down into the top of the board rather than into the side.

The type of board can vary. Plain wood, pressure treated or my fav plastic deck material. I rip down the decking to about 1"x1". Sometimes I use a full wood 2x4 pressure treated.

For curves I use bender board, again I prefer plastic but wood is fine. I rip down the plastic bender board to a 1-2" width. I put on 2 or 3 ply (layers) and the when nailing the nail just goes between the plys when nailed from the top and I use a 3/4" nail then. Nailing from the side requires more plys so I don't see the point of that.

I like using concrete screws because they last and are easier than epoxy. But epoxy can be used. For epoxy you have to brace the piece while the epoxy cures which is a pain. A combination does work well, a few screws where you can and then epoxy any loose places and the screws hold the board in place. You can also push a bit of cloth into gaps to keep the epoxy from flowing down and out the bottom. You can also cover a bit of cloth in epoxy and shove that into gaps.

It does not require a strong structure. The weight of the water will push the liner against the concrete and nail it into place, you can't move it pulling as hard as you like. The only thing that's needed is to stop the loose liner above the water from flopping over into the pond.

There isn't a great glue for attaching EPDM to concrete. It just doesn't last very long.

Depending on the rock at the top I'd bust them out, lay the liner and then mortar the rocks back into place.

I normally mortar over the liner, or mortar rock over the liner. In this case the mortar can be enough to stop the liner from flopping over. However, I prefer attaching a plastic board, nailing the liner and then mortaring over it all. I think that lasts longer and is easier to do even though it may sound harder.

In all cases I don't nail liner until after the pond is full. This requires the liner to be larger than needed, but that's normally not a problem.

I should make clear that I personally would probably not go to all this trouble of trying to attach a liner in most cases. It depends on the depth of the current pond, thickness of current concrete, etc. In almost all cases it is way, way easier to remove the current structure, make a concrete block collar, lay the liner and then optionally mortar rock over the liner.

Whether the gravel beneath is dug out depends on the desired depth, local climate, owner's goals, etc.

I reuse all the removed material to build other landscape features so it doesn't have to be land filled. Reuse the rocks in the new pond.

Or I'd remove the pond completely.

Someone before you created a poorly built pond. It happens, a lot. Many people look at something like this and think it's a pond...it isn't. It's a hole with some concrtete...that's it. No reason for you to be saddled with the work, expense and unending frustration of having to deal with their sloppiness. Remove it, rebuild it, enjoy it.

I really do appreciate the detailed instructions and voice from experience from waterbug. However, I was able to fix the crack with hydraulic cement and the pond and waterfall are now holding water. It may not turn out to be as maintenance or aggravation free as a reconstructed liner would, but the fix was inexpensive and fast. It won't be difficult to do again when the next crack appears (you don't even have to empty the water to use the hydraulic cement). I don't consider the stone pond and waterfall I inherited to be a "hole with concrete." It took artistry and heavy labor and gave previous owners great pleasure for many years. Those of us who like old houses -- and their ponds -- are willing to put up with their special needs:) So thanks everyone, and please let my experience be a lesson in taking a chance on keeping it simple.

It's always impossible to tell from a few posts the best course of action, people are very different. I'm glad it worked for you and I hope the repair lasts for many years and it may.

But of course it could fail next week, next month, next year, next century. It's impossible to tell. And that's OK with you so that's cool, certainly nothing wrong with that. Or the amount of water loss from tiny cracks or thru the cement is perfectly acceptable. Nothing wrong with that either. Any pond kept in service for no matter how long is a good pond in my book.