Running 3/4" cndt is good advice. Also, consider running the next size up wire (or calculate it). In your case your only going 20ft from the house - not bad.
In some cases it the run could be a couple of hundred feet - if the service panel is on the other side of the house and you have to go around a few things on the way to the pool pump. This all has to do with voltage drop. Many homes have low voltage at the service drop already. It can be within ANSI spec and still be too low to allow you to drop much more and still serve high loads.
