In saucepan add water and celery; bring to a boil; reduce heat and cook until celery is very tender; drain.
In a separate saucepan add butter and melt. Add flour; stir. Slowly add 1 cup milk; stir until thick.
Spoon celery into a sieve over a bowl; push celery through using a spoon. Discard anything in the sieve.
Pour into the saucepan with the milk mixture the drained celery. Add salt, pepper and celery salt; stir. Keep heat on simmer, and simmer 10 minutes. Add 1 cup of hot milk to the soup and stir until the soup is hot.