Rinsing ground beef is retarded. If you are worried about the fat content, go to a real butcher shop (where you should be getting meat from anyway) and pick out the leanest piece of meat you can find (usually eye of round) and have them grind it for you.
I grind meat myself. If anyone wants to eat the best burger they should start doing so. I grind 50:25:25 blend of sirloin, chuck, and brisket or 50:25:25 Short Rib, Chuck, Brisket.
Or for the Ultimate Burger, go with the Blue Label Blend-
6 ounces beef sirloin, trimmed of gristle, and cut into 1-inch cubes
5 ounces beef brisket, trimmed of gristle, and cut into 1-inch cubes
12 ounces oxtail, fat and meat carefully removed from bone and trimmed of silverskin, bones discarded or reserved for another use (about 5 ounces of combined meat and fat)
Procedure (Meat Grinder)