nice idea, especially if its just a water change and not cleaning gravel, can be cleaning another tank while one is draining, would save me sometime for sure
I just use a cheap 1000gph China made water pump from a lfs here and 25ft of 1" tubing to drain and the python for picking up the crap from the bottom and move to the next tank. you can find a bunch of cheap pumps on Ebay and whats better yet you can use it on bottom tanks.
This is a cool idea, I am thinking about building one of these for my bare bottom tanks and put the 90 on the bottom of the tank and drill a hole 4" or so from the top so I can suck the water from the bottom and once the water gets low enough will break syphon.