Tank Leak help

[jdhuyvetter]

I've got a 300 gallon tank, 96 x 30 x25. I recently drained it to convert to a freshwater plant tank (never fear, still have the other 300 reef). Anyway, drained it to pull the last of the rock and sand out. Filled it back up with freshwater and 20 gallons of vinegar. Ran it for a week when I went to MACNA. Labor day, I drained it back down and cleaned all the glass. It was empty and dry for about a week while I silicone some tile in for a background and slate to the bottom to build some plant terraces. Filled it hallway back up for a few days to let the driftwood soak. Then, filled it all the way back up and turned on the sump. Started leaking at the bulkheads and back corner. Since the bulkheads were leaking, I assumed that was the problem. Drained it back to about an inch below the overflow and let it sit for a week. This weekend pulled the plumbing from underneath, resealed the bulkheads, replumbed the sump and topped it back off. Bulkheads are completely dry and both back corners are leaking. Tanks is completely dry. Water is coming from the bottom.

Tank was not cracked when I drained and cleaned. It has a double glass bottom and is euro braced around the edges (top and bottom). So, where the water is, that means there is a triple layer of glass on the bottom.

 

[jdhuyvetter]

Just had a thought. When the bulkheads leaked, I sealed them from the bottom. I did not pull them and replace the gasket or seal them from the top. If the tank has a double bottom, is it possible that the bulkhead is leaking between the glass and then leaking out the corner?

Pic of the tank cleaned with new background before I filled it back up. You can clearly see the double bottom and bracing around the overflow.

 

[kmbyrnes]

Hard to tell from the pic. Is that second glass pane sealed perfectly to the first?
If not water can be seeping between the plates and NO bulkhead will seal that forever.

 

[jdhuyvetter]

There was water between the glass. So, siliconed the inside of the bulkhead hole. Silicone went in about 1/8 inch. Then, put bulkheads back in with a bead of silicone around the base for extra measure. Fortunately, these bulkheads are not under pressure. So, hopefully this will solve the problem. First two pics show the water and gunk between the glass. Last pic is the silicone bead I was able to force between the glass.