I had a small leak in one side of the overflow in my 180g once. The only problem I thought it may be was as mentioned, seeping between the stack and bulkhead portion during long shutdowns, for whatever reason. I sealed the stack with plumbing tape and it was fine. If you glued yours, thats even better.
I dont see how it can run into the sump any different than normal in that case?
I must say, it always did bug me though, thinking it could all leak out somehow.
