Place enough water in a 5-quart pot over high heat to boil the pasta. Place the bouillon in the water & bring to a boil. Place the rotini in the boiling water & cook according to package directions. Drain & set pasta aside.
In a large pot over high heat, combine the chicken broth & water. To this, add the celery, onion, carrots & chicken. Bring to a boil & stir in the reserved pasta. Reduce heat to medium-low, let simmer & season with the garlic powder, onion powder, & salt & pepper to taste. Cook 20 minutes, or until vegetables are tender & chicken is no longer pink. Serve hot.