Crumble ground beef into a large skillet or Dutch oven with lid. Add onion, chili powder and garlic powder. Stir well, using a wooden spoon, until combined. Cook over medium-high heat for about 5 minutes, until no pink remains. Drain, using a colander. Stir in stew tomatoes and water. Bring to boil. Simmer with a lid on for 5 minutes. Stir in rotini. Put the lid back on and continue to simmer 10 to 12 minutes, or until rotini is tender.