Not trying to be difficult but broke off what "connection" to the gray tank? In the first post it was a valve that was might keep it from draining...that's one thing. A "connection" is a different matter. Is it a gray tank that has a separate drain from the other gray tank? The "connection" that you connect the hose to? There are the connections to the top of the tank that whatever is plumbed to so they drain into the tank. There is the "connection" to drain the tank and a connection for the bayonet end of the drain hose to attach to. What are we talking about?
If the trailer is plumbed into 2 different gray tanks and they both have their own "dumps" to connect to a hose and he has broken that end connection he needs to fix it. To get what is draining into tank a to drain to tank b you need to replumb the trailer. If it is the "connection" on the utility side he should be able to fix that.
Edit: Looks like Chuck and I were typing at the same time. He said the same thing in a lot less words.