Fill the pot with enough white vinegar to cover the showerhead. The acids in the vinegar will help dissolve the white mineral deposits on the showerhead. Let the showerhead soak in the vinegar for 30 minutes to overnight. The more soiled the showerhead is, the longer you will have to leave it in the vinegar. If you are in a hurry, and if the showerhead is made from metal, you can place the pot on the stove and simmer the vinegar for 15 minutes.