Add whole potatoes and 2 tbsp salt to a large pot. Cover with cold water and over medium high heat, bring to a slow boil. Boil potatoes until they are fork tender, about 20-25 minutes.
Allow potatoes to cool. Peel them and cut them into bite sized pieces.
Add the eggs to a saucepan and cover with cold water.
Over high heat, bring the eggs to a boil. When the eggs have come to a boil, cover, remove from heat and let sit for 15 minutes. Remove them from the pan and let them cool.
When eggs have cooled, peel and chop into small pieces.
In a large bowl, combine onion, celery, relish, 1 tsp salt, pepper, mayonnaise and mustard.
Add potatoes and eggs and gently mix until potatoes are coated.
Taste and add additional salt or pepper, if needed.
Cover and refrigerate for at least one hour and up to 24 hours before serving.