Put the potatoes in a large saucepan; cover with water and add 2 teaspoons of salt. Place the pan over high heat and bring to a boil. Reduce the heat to medium-low, cover the pan, and cook for about 15 to 20 minutes, or until the potatoes are tender. Drain and set aside to cool.
When the potatoes have cooled, put them in a large bowl. Add the celery, red onion, and hard-boiled eggs.
In a small bowl, combine the pickle and juice, 1/2 cup of mayonnaise, and 1 teaspoon of mustard. Add 1/4 teaspoon of salt and the pepper. Blend well.
Gently stir the dressing mixture into the potato mixture. Add more mayonnaise or mustard, as needed, and adjust seasonings, to taste.