Heat the butter in a large pot or Dutch oven over medium heat. Add the onion, celery, and red pepper and cook, stirring occasionally, for 8 minutes, or until softened. Stir in the garlic, then add the water, potatoes, Old Bay, salt, thyme, paprika, bay leaf, cayenne, several grinds of pepper, and the corn cobs. Simmer for 20 minutes.