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