Worst Case Scenario - Black Water Tank Leaking

Well, I opened up the bottom.

I filled up the tank all the way to the bowl of the toilet and NO LEAK!

Unreal. Sewage was dripping out of the bottom of the TC last time my girlfriend flushed.

We stopped using the tank for about a week, keeping it empty. I rapidly poured a full tank of fresh water into it through the toilet. 6 gallons at a time.

Now no drips.

I'm lost.