Please HELP - Liner Leak

[tanyaclick]

Hey guys, I've had a leak in my pond for several months and wanted to finally post about it. I'll admit I put this off out of embarrassment — here's the full story.

There was a small fold of liner tucked right at the base of a big boulder (this pond is a multi-tier hillside waterfall — the liner runs up under the waterfall rock tiers. The liner under the bottom boulder folds back on itself. That fold was flopping out and catching the waterfall flow. I asked the landscape company that built the pond whether it was part of the actual liner or just extra padding. I was told it was padding, so I cut it off. It wasn't padding — it was the fold itself, so cutting it opened up a slice right at the base of the rock which is fully submerged

First repair attempt (failed): They used 3" double-sided EPDM liner seam tape to bond the two cut edges together like a sandwich, then a 5" wide EPDM liner cover seam tape wrapped over the top and bottom of that seam. Before that, they used a special liner cleaner/conditioner to prep the surface, which made it tacky before laying the tape down. They also rolled Flex Seal over the edges. Before long, water started peeling up the flex seal and tape edges and got in between the layers, and the leak came right back.

Proposed next repair:
4A — Tuck the bottom piece back under the rock (shorter), and let the top piece extend past it and fold down over it— a real bib/overlap, not just two flat edges taped together. Tape over that overlap.
4B — Add a separate patch piece of liner over that seam, taped around all its edges.
4C — Roll a liquid seal (something like "HLF 5000" — contractor couldn't recall the exact name) over the whole patched area. This is a rolled-on liquid seal, not tape or adhesive.
4D — Take one more oversized piece of liner and tuck it fully in under the rock, bonded by that liquid seal underneath it.


What I'm hoping to find out:
Does layered tape (even good EPDM seam tape + surface conditioner) ever actually hold long-term on a seam like this, or is this kind of spot just doomed to keep failing no matter what tape is used?

Has anyone had luck with EternaBond EternaPrime or a similar contact-adhesive/liquid-seal product for a spot like this?

Ripping out and rebuilding the whole waterfall to run one continuous liner piece would be a massive expense, so I really want to avoid that if at all possible. But I'm also done getting nickel-and-dimed on repeated failed patch attempts that are already costing me a ton of money.

So honestly — what is the one, 100% reliable, decades-lasting fix for a seam like this?
Even with a full rebuild and a giant continuous liner, there will still be an edge somewhere up top, since the sides would be submerged either way and only the top edge is exposed to flow/splash. Is there really any way to avoid having a vulnerable edge at all, or is that just an unavoidable reality of how these waterfall liners work?
If anyone's dealt with a leak like this and found something that actually held for good, I'd really appreciate hearing what you used and how you applied it. Photos/diagram below.

 

[GBBUDD]

Unfortunately from my phone i cant read yoir diagrams. But looking at you build im not seeing any waterfall foam or rocks tucked in the spaces that would be hidi g the foam.
These type of builds are very hard to co trol water flow and as the pond ages debris, roots, and even algae can push down on liners block the easiest path for the water to take thus diverti g it else where. And probabky why your now having issues. I should Also add settling. To be honest you can try to install waterfall foam trying to keep the water runni g down the center of your falls instead of making its way under the rocks and creating leaks. This has probsly a 40 percent chance of fully stopping your leaj the foam is not waterproif but it direts 90 % of the wayer where you want it to go.

If it was me id pull it appart and rebuild it using the foam, bib liners and even some caulking if need be. Lots of videos online to show you how to build a more successful waterfal.

Rule one waterfalls are erossion. And cut into the hiĺl side not built up on the hill side.

Most leaks are due to a low edge usualy from walking around the pond or weeding. Then you get your blockages and growth