Start by prepping your vegetables. Dice the celery, onion, carrot, potato, and bell pepper into 1/4-1/2″ pieces. Set them aside for sautéing.
Heat a Dutch oven over medium-high heat, and add 3 tablespoons of olive oil. Once the oil is hot, toss in the diced celery, carrot, onion, potato, and red pepper. Sauté for about 5 minutes until the vegetables start to soften.
Next, add the drained and chopped tomatoes, parsley, oregano, garlic, and red pepper flakes. Stir everything together, allowing the flavors to meld.
Pour in the 5 cups of water and 2 cups of chicken broth. Cover the pot and bring the soup to a boil over medium-low heat. Once it boils, partially cover the pot and let it simmer for 1 hour.
After simmering for an hour, use a potato masher to lightly mash some of the vegetables at the bottom of the pot. This step adds thickness to the broth while leaving chunks for texture.
Stir in the 2 cups of shredded chicken and allow the soup to simmer for an additional 30 minutes. This infuses the broth with even more savory goodness from the chicken.
While the soup is simmering, cook 2 cups of ditali pasta according to the package instructions. Drain and set aside.
Right before serving, stir the cooked pasta into the soup. For an added touch, serve with freshly grated Parmesan.