Place potatoes in pressure cooker with water. Cook on high pressure 3 minutes. If potatoes are larger, cook for 4 minutes. Let steam release for 3 minutes. Then quickly release pressure and open cooker. Peel and dice potatoes when they are cool enough to handle.
Alternate layers of potatoes, onion, and celery in a large bowl. Season each layer with salt and pepper. Top with the chopped egg and sprinkle with dill.
Mix together the mayonnaise, mustard, and cider vinegar in a small bowl. Gently fold the mayonnaise mixture into the potatoes. Chill at least one hour before serving.