[JRTJH]

The only way you're going to know "how bad it is" is to pull down a part of the coroplast and take a look. Realistically, you aren't "supposed to be able to" rupture your tank. The vent stack on the roof will overflow before you pressurize to the point of rupturing the black tank.... So, chances are what you did is push the hose off the black tank flush fitting on the black tank and filled the coroplast full of water. Once it reached a certain weight, it popped the coroplast (the BOOM) and water flowed out. As you pulled the RV, every time you stopped or accelerated, water would flow to the hole in the coroplast and flow out.

Crawl under your RV, pull a few of the screws holding the coroplast in place next to the tank, stick your head and a flashlight in and see what you find.

Good luck !!!!!