Re: Deal with two problems with one solution (no puns intended).
"you'd need a powerful hoover to suck up water through a tube thousands of miles long."
engineering 101 would say that you have to have a pump with a pressure of 1000s of miles of water. It's about 2 feet per psi so that works out to about 2500 psi per mile, or 2.5 million PSI for 1000 miles of water. Mutliply that out for 'thousands' and you have one HELL of a pump!
However, as you get away from the earth, gravity diminishes based on 1/r^2. The earth is around 8000 miles in diameter, so 4000 mile radius. So at 4000 miles away from the surface, gravity actually drops by a factor of 4. And the closer to the moon you get, the more the moon's gravity will affect it, too. So now this becomes a calculus problem involving the total weight of a column of water several thousand miles long, and I don't want to do the math (though when you get to the point where moon/earth gravity are balancing one another, it's all "downhill" from there).
/me points out you can't suck water past a vacuum, which would be around 30 feet of water. To get water to go up more than 30 feet, you either need capillary action [like in a tree], or a pump at the bottom.