Yesterday I replaced the fill valve, flush valve, and handle. It looks like the toilet tank might have a very tiny crack in the bottom. The crack is running from front to back. It’s very thin, and hardly visible, I’m not even sure that it is a crack that runs all the way through. If it is a crack, I think might have overtightened one of the bolts that mount the tank to the bowl since the crack runs right through it.

The tank and bowl are yellow, so it will be hard to find a replacement tank in the same color, so if possible I want to repair it if possible. Is there a product that can repair the crack? Some sort of expoxy or glue or something like that?

Also is there any way to confirm that the crack is what is leaking and not something else? Thanks a lot for any advice!

From your description it sounds like you cracked it. To test for leaking you’ll want to dye the water with either some blue food coloring or an actual dye tablet. I don’t suggest trying to repair a cracked tank. Body weight and temperature variances may cause it to grow or expand over time. And you don’t want to be away from home with a leaking tank. Your best bet is to replace it.