Cut the potatoes into about 3/4 inch chunks and place them in a large pot of cold water, (make sure they are covered by at least an inch.) Sprinkle with 2 tsp salt.
Bring the pot of potatoes to a boil over high heat, then reduce the heat to medium and let simmer for 8-10 minutes, or until fork tender. Drain and then let cool in the colander for about 20-30 minutes, giving it a light toss or shake every now and then to let any steam escape.
For the dressing: In a large mixing bowl, stir together the mayonnaise, relish, apple cider vinegar, sugar, both mustards, celery seeds, chopped dill, salt, and pepper until well combined.
Add the diced hard boiled eggs, red onion and celery, then stir gently until it's all evenly combined. Add the potatoes and toss until completely coated.
Cover the potato salad with plastic wrap or a lid, then refrigerate for at least 4 hours before serving.