Decryption of a password is never needed. And no one is supposed to know any passwords, no matter how much permission a person has. Only one person in the world should know the password: the owner of it, the one who created a password.
You may ask, how authentication is possible then? Well, think a bit, perhaps you can understand the schema. Not yet?
[EDIT]
I've explained this matter in my past answers:
storing password value int sql server with secure way[
^],
Decryption of Encrypted Password[
^].
—SA