Boil potatoes with skin on for about 20 minutes. Drain, allow to cool, peel, and slice thickly. Set aside.
Fry bacon and crumble; reserve the bacon fat.
Mix water, vinegar, pepper, salt, and sugar in a saucepan and simmer for 10 minutes.
Combine potato slices, bacon crumbles, bacon fat, green onions, and parsley in a large bowl. Add the water-vinegar mixture slowly; you may not need all of the liquid.
Toss all ingredients together, add oil slowly, and refrigerate 5–7 hours. Stir occasionally and add more liquid as needed.
Serve with bratwurst and kraut for a complete meal solution!
