I've made 3 smaller "patio ponds" out of various materials that I have scrounged up. Depending upon the size of pond you want to create, some of these techniques may be useful to you. 2 of my ponds get dismantled for winter and the fish are overwintered inside the house in a large aquarium. My smallest pond is made from wood shipping pallets that I got from work and a shower curtain liner. I measured the liner and decided on a size and depth to cut the wood to. I built a basic solid box out of 2x4s that was approximately 2' tall and 4'x4'. I finished the top edge with a 2x6 and stained it. Each spring I go buy a new curtain liner and staple it to the inside edge. Add water and a pump and you're finished. The 2nd pond is built in a somewhat similar fashion, with lumber I repurposed after tearing out an old deck. I built 8 boxes (about 2'x2'x2') that served as the 8 angles of my octagon. I then attached 2x6s between the corners of each set of boxes, creating one large octagon. I bought a huge roll of the thickest plastic drop cloth I could find, lined the inside twice, and stapled the edges. The 8 boxes were filled with potting mix and planted with flowers. I added a pump and fountain, and it works great. Again, this gets dismantled in the fall, and the fish are brought inside. It's so shallow it will freeze solid otherwise. New liner every year, also. My third pond is built out of chunks of concrete torn out when we re-did the sidewalks. This one is permanent. It sits on dirt, so I did dig down just a little bit to increase the depth of the pond and also to get the lowest layer of concrete below ground level. I just mortared the concrete chunks together as I built the wall up to the desired height. Once I was close to the desired height, I put the pond liner in (yes, I actually spent money on a REAL pond liner. LOL!) and then placed more concrete chunks on top of the edges of the liner to hide it and give it a more finished look. I looked up a concoction containing yogurt and ground up moss on the internet, made it and covered the concrete with it. It's starting to grow a little bit, which gives it all a more weathered look. Add water, fish, and a pump.....Viola! Those are my creations! Other than the pumps, I really have a minimal amount of money invested in each. They aren't award-winning by any means, but I think they add a lot to my otherwise bare patio areas.

Unfortunately these fixes are not viable. These things can reduce the leaking in the short term. Fiberglass, if made thick enough would work for some period of time, but even that is likely to fail. Saw a large water feature where that was tried many years ago and it was a complete failure. Partly because it was ugly, partly because it still leaked. Plus fiberglass would be very expensive compared to just rebuilding correctly so I don't consider that to be viable. The problem is the foundation, basically a pile of rocks that is falling apart. Nothing is going to hold that together. Say you injected very crack with epoxy, that would fix it...until it developed more cracks. The other issue is non-leaking waterfalls are difficult to build even when done correctly. Not hard, not impossible, but it requires some level of detail that many people chose to ignore. Water rarely takes the path we expect. For example water can move up hill in a waterfall. Tearing down the waterfall and rebuilding is far less work imo and gives you the best chance of success. You can reuse the current rock and you don't have to clean off all the existing mortar as it will blend in or the few bits that stand out can always be cleaned up later if they bug you. My suggestion is tear it all down. Breaking mortar and concrete is all about litttle taps, not big powerful swing. Vibration breaks mortar. You don't need or want a huge sledgehammer, a small light hammer is fine. A chisel is the main tool, normally called a "cold chisel". You want the smallest tip and longest you can fine even if you have to order online. Something like 1" wide tip and 18" long is good. Long because it can be used as a pry too and it keeps your hands further from the rock which is safer. My best chisel for this is 16" long and comes to a point, I think it's a center punch. And of course a air powered chisel works well too but you need an air compressor. You can buy air hammer chisels and just use by hand. Safety goggles unless you like grit in you eyes and trips to the eye doctor. Once removed you want to start with a good foundation. For 7' foot high you really want a poured concrete pad with rebar, like 6" thick and below the frost line. Above the frost line isn't super bad so that's a corner that can be cut. You can do away with the pad and just use concrete block, basically make a pad out of blocks filled with concrete. You do want this all on undisturbed soil, not back fill. Create the basic shape you want with block keeping in mind the rock veneer will be thick. Underlayment over the block and then EPDM liner. Mortar rock over that. To build leak free think always assume there will be a leak. Suppose you get done and this thing leaks...how do you find the leak? In most cases it's impossible because the liner is completely covered. The leak is almost always water moving beyond the liner, not a hole. So all we care about is the edge of the liner right? I build so the edge of the liner is exposed. When I'm done you can see the contiguous cut edge of the liner. So there's rocks outside the liner and rocks inside the liner, but at no point do they meet. Eliminates wicking (water running up hill). I test the falls with running water and can see exactly how close water is coming to the liner edge because I know exactly where that edge is. I can make adjustments. When happy I mortar a little rock over the liner edge, or a combination of real and fake rock, just enough to hide. OK if some is exposed because it's so thin a line you just have to break up the pattern a little. If you ever have a leak in the future this thin covering can be removed to check for leaks.

Hi Apparently you intend to grow the plants directly on the bottom? IME almost all water plants are VERY invasive . Growing in containers goes a long way toward avoidiing a lot of problems. makes arranging and fertilizing MUCh easier also and a backsaver when a cleanout is needed. Only plant I've had make it through the liner is "Strangler fig" but then I've seen them penetrate driveways lol. gary

Glad I can help, but I don't want to overstep my experience, so I will answer the questions where I have some hands on knowledge. Bottom drains - they will sweep any sand in the immediate vicinity, but have no effect on things a foot or two away as the velocity is negligible. The idea is to get solids to fall to the lowest point and get swept away. If the solids sit in rock crevices two feet away, they stay there. This is the source of the "rock bottm vs smooth bottom" discussion. River rounds - if you have them available, great. If you have to buy them by the bag, you are going to spend a lot to cover a 9000 gal pond. You understand the tradeoffs here- smooth doesn't stack well, but othewise is great. I doubt you can get anything over 30% with rounded stones. There are actually engineering formulae for determining the max stack angle for differnt shapes and density of material, but I don't think pond builders worry about them. Any slope that goes to the edge can be used by raccoons and herons. I find that having a deep pond where the fish can get away from predators helps a lot. I haven't used overhanging rocks. Sand is graded by size, source, and shape. You want a "sharp" builders sand for it's ability to pack. Playbox sand is usually too fine and rounded. Not the most critical issue however. Overhanging deck - a great Japanese design style that works the wonderful contrasts between man made/natural; linear/irregular; water/land; static/changing and many others. See my posts for one example. I use Ipe because it weathers to a beautiful grey, doesn't need any maintenance or finish, and doesn't contain any toxic metals to drip into the water. It has natural toxins of course which make it durable, but I don't let too much in the water. I have dropped a few pieces in by accident (it sinks like a stone) and haven't noticed any effect. I hope the rising water table and tree limbs don't damage the liner. Swimming pool installers (gunite and liner) often use a reverse drain valve meant to allow water in if the pressure is higher than the pool. The big tree limbs probably won't penetrate a rock lined pool but what about the roots? could be an issue digging and in the future. Good luck.