Cover the potatoes with water and 1 teaspoon of salt in a big pot. Bring to a boil over medium-high heat then lower the heat to simmer and continue cooking for 12-15 minutes or until tender. Drain the potatoes, let them cool down and chopped.
In a medium bowl, stir in Mayo, mustard, apple cider vinegar, paprika, 1/4 teaspoon of salt and (optional) black pepper.
In a large mixing bowl, add the chopped potatoes, chopped celery, chopped onion and stir in the mayo-based dressing. Add sweet relish, keep stirring until well combined.
Cover the bowl with a plastic wrap and store in the fridge for at least an hour before serving.