To turn off the steam in the bathroom you will need to use a handle that is found in the East Office on the first floor of Raccoon City Police Department. To get this handle in Leon’s play through you’re going to need to have gotten the bolt-cutters. In the first play through with Leon you will get this item once you’ve progressed to the fire escape and met back up with Claire for the first time.
Once you have the bolt-cutters you can access the East Office area on the east side of the Police Station. The handle that turns off the steam in the Shower Room will be sitting on a table in the East Office.
Once you have gotten the Handle, you’re going to want to go back over the west side of the Police Department and attach the handle to the pipe to turn off the steam. Once you do, you will be able to walk into this area and reach other parts of the second floor, including the S.T.A.R.S. Office, Armory, and Linen Room.