Slice a large sweet onion into discs and drop them into the bottom of a slow cooker.
Sprinkle the pork loin on all sides with salt and pepper and place it on top of the onions in the crockpot.
Cover and cook on low for six to eight hours or until the pork is falling apart.
About an hour before you want to eat, combine the ketchup, Worcestershire sauce, chili powder, salt, hot sauce and water in a medium-size saucepan over medium heat. Heat to boiling and boil one minute.
With two forks, shred the pork and mix in the onions.
Pour about a cup of the sauce over the pork (or to taste) and use the fork to mix it inches Reserve the remaining sauce to serve with the pork sandwiches.
Cover and continue to cook for another 30 to 45 minutes. Serve on a roll with the remaining barbecue sauce and your favorite sides.