Cheesy Potato Soup

I know a couple of other people have posted similar recipes, but this one is really yummy too! I was looking for one that didn't require chicken broth, and found this! It's best with a yellow/gold potato, and it definitely needed salt....but GREAT flavor! I've also served it in homemade bread bowls.

INGREDIENTS
6 tablespoons butter
1 1/2 cups chopped onions
1 1/2 cups chopped celery
4 cups water
8 potatoes, peeled and cubed (I use yukon golds)
15 slices American cheese - broken into pieces
4 tablespoons all-purpose flour
2 1/3 cups milk

Melt the butter in a large pot over medium heat. Saute the onions and celery in the butter for 5 to 10 minutes, or until tender.
Stir in the water and potatoes, bring to a boil and then simmer until the potatoes are tender. Add the cheese and stir until melted.
In a separate small bowl, combine the flour and the milk and stir well until the flour is mostly dissolved. Pour this into the soup slowly, stirring constantly, until soup has thickened, about 5 minutes.