Bring the water and 1 teaspoon of the salt to a boil in a saucepan over medium-high heat. Add the green beans and potatoes. When the water returns to a boil, reduce the heat to a simmer, cover the pan, and let cook until the potatoes are tender, about 10-12 minutes. Drain well and set aside. Heat a large skillet over medium-high heat. Add the bacon and onion and cook until the bacon is crisp. Drain off all but 1 tablespoon of the bacon grease. Add the drained beans and potatoes to the skillet and stir to coat them in the bacon and onion mixture. Season with the remaining salt and pepper. Serve immediately.