Do you mean the tank overflowing? The only way I see that happening is if the drain or overflow box gets clogged and the return pump pushes all thew water from the sump into the DT. Or,if you have an ATO and it malfunctions and dumps a bunch of fresh water in the system.
"when it happens, dont pannic, just take your shirt off, draw a spongebob face on your chest, and run down your neighborhood with your hands in the air screaming help help!!