When you drill, you run the risk of cracking the tank.
I like to keep water in the false bottom so that I can have a water feature where my frogs can leave tads. I just siphon water from the water area using aquarium tubing (the stuff people use for air stones). Since i don't do this regularly, I don't include it in the setup. I just siphon the water (using the suck and gravity method).
I use a siphon method on mine. I put a piece of pvc that goes through the substrate to the false bottom which has a very well 'carved' rock that sets atop of it. When ever the water needs removed (i have only had to do this once in a year) i just move the rock and put some aquarium tubing down through the pvc pipe and pishon it out.