1500 Gallon plywood build leak test

[Zkris28]

Evening all, any tips to locating a leak on a fresh plywood build?
Build 12x5x4 tall, stacked 2x4 frame interlocking corners with 3/4 inch plywood and fiberglass in all seams. I used around 7 gallons of max ACR to seal, around 2200 epoxy coated screws and around 10 tubes of silicone for the 11x3x3 panel bondo for all screw holes and ACR thixotropic for fillets.
When I filled for the leak test I had the tiniest of leak in the bottom right zone of the tank that I can't seem to locate.
It is near the glass silicone seam height, the glass panel rest 4.5 inche above floor height of the tank on the 3/4 inch plywood in which is framed around the glass so they're level with eachother. There is no water exit on the opposite side of the panel on the outside.
So far I've emptied and checked for water under silicone, no signs.. I Used 1 sideded pond tape to seal over the panel seem to the plywood from the glass, and refilled to same height and leak was still present at same rate.
I then sanded down the front section on the bottom and the corners and reapplied pond shield to some minor questionable areas and the rest of the front bottom section of the frame, and the leak was still present, I'm thinking it still may be a silicone leak regardless of the pond seam tape being applied.

Part of my original plan was fiberglass and epoxy the where the glass and plywood frame meet, but based off common knowledge you don't typically want to cover silicone.. I'm thinking however in the case of these build with the silicone really just being a gasket for the glass, it would be safe to remove the tape and fiberglass epoxy all the panel seam where plywood meets silicone/glass.. Thought on this?

As a side note Between first and second fills I used red food coloring to attempt to locate point of water exit, but the leak is to slow for that to be effective.
With that being said perhaps, should I try for a complete fill to see if the leak slows or worsens? I feel like that may be an indicator as to wether it's an epoxy leak, or silicone leak due to pressure changes.
I'm really struggling to get this figured out as my basement is currently stripped waiting for this tank to finish the remodel, as it's behind a wall and the end goal is to frame it behind the wall when the rooms is finished.. Time line worsens with our first baby on the way in January and I'm really wanting to be able to focus on family time by then, and this is driving me insane! Lol

 

[Zkris28]

Will try to get better pictures for everyone when I get home incase we get it up and running!

Plan is a floor level sump around the perimeter.. water lines and drains are already setup to drip to tank, and purge to French drains out in the yard from the PVC in the last picture.

 

[Texasrockwell]

Can you get a picture of the glass from the inside ? And your panel is 3 inches thick?

 

[Zkris28]

I can. Sorry, the old tank itself that I used for the panel was a 11'x3'x3'.. The glass itself is a 11'x3'x0.75" lol

 

[M1A1]

Part of my original plan was fiberglass and epoxy the where the glass and plywood frame meet, but based off common knowledge you don't typically want to cover silicone.. I'm thinking however in the case of these build with the silicone really just being a gasket for the glass, it would be safe to remove the tape and fiberglass epoxy all the panel seam where plywood meets silicone/glass.. Thought on this?

I don't think it will be easy to get epoxy to stick to silicone but I'll admit I've never actually tried it.

Photos of the the tank exactly where the suspected leak is would be great, inside and outside so we can see what you're seeing.

Did you fill the tank in stages or all in one go? What was the water level when you noticed the leak?

 

[Zkris28]

1/3 water level and I stopped before touch ups.
This last time I stopped about halfway due to getting distracted. I'll get more photos when I get home.

The thought process isn't necessarily stick the epoxy to the silicone, but more so use the fiberglass to hold the epoxy in place overtop while it cures.. However silicone cures to epoxy well, so I imagine the opposite is roughly the same

 

[Zkris28]

Here's some additional pictures now that I'm home.
The white residue all over the epoxy is dust, drywall, etc.. Was going to clean her out after well water leak test before I put fish water in

Pond seam tape was added after initial leak was located to see if it would affect the leak any so I could figure out if it was a seam or not.

It's hard to see the lateral boards in the front behind the wall that were wet because they're drying out. The second board down is not wet, that's residual epoxy. The majority of the water is located 5 boards down on the front, possible starting at 4th board down.. It almost seems to be too low of a leak for it to be the silicone gasket, but at the same time I applied 6 layers of clear epoxy before starting the 1 layer of black ( I should've used more black, as the transparency shows through because I ran short on coloring, but it's the bottom so I'm not entirely worried about the appearance of that section lol) so I'm not sure where to start here besides guess and check.

I did attempt to put a bottle of food coloring in the standing water to where it went but the leak isn't large enough to pull any noticeable amount of water or dye through.

 

[Texasrockwell]

Did you set the panel flat against the tank or did you inset the panel?

 

[Zkris28]

Did you set the panel flat against the tank or did you inset the panel?

Inset within 3/4 inch plywood, which is also epoxied.

 

[Texasrockwell]

Nice build by the way. I am not sure there is going to be a way to find the leak if it is pin hole size. I had some issues with a panel leaking and unfortunately I had to remove it and reseal it. If its not the seal, then you may have to do more layers of Pond Armor ( or whatever the black stuff is.) Last plywood tank I did, I used 4 layers of Pond Armor. It had a tiny leak that I couldn't find when I had 2 layers on, so I did 2 more coats to be safe.
Maybe someone else will chime in with an idea to help find the leak, but otherwise its trial and error.