H2O in Exhaust

Ray, you've got problems mate!
Get the vehicle checked out by a decent mechanic with a scanalizer to read the problem code.
Look around the engine bay for any tell tale signs of coolant leaks, like staining on hoses, or down the side of the head.
Water out of the exhaust? You will get water (very small amount) on short trips from the exhaust as this is a normal by product of combustion, but there's no way I can think of that 3/4 gallon can enter the exhaust.
I'd be betting the heads warped or the cooling system has a leak.
I wouldn't be driving it until it's checked out.
Best wishes.

Ken.