Step 2 · Create an Access Panel
To access the plumbing, you will need to create an opening in the wall behind the shower. Use a stud finder to locate the studs on either side of the plumbing area. Mark a rectangular area for your access panel, typically about 12-16 inches wide and tall enough to comfortably work. Use a utility knife to score the outline, and then use a drywall saw to carefully cut out the panel. Set the removed piece of drywall aside, as you can use it to patch the wall later.