Moving a shower, adding a second sink, or converting a tub to a walk-in all start with the plumbing behind the wall, not the tile in front of it. Rough-in work, drain and vent relocation, and supply lines all have to be right in Chula Vista, CA before any finish work goes on.
Before work starts, confirm which walls carry plumbing so nothing gets opened up blind, and keep the water shut off in any area under active work. Stop and call if a pressure test reveals a leak, a drain relocation changes the slope needed for proper flow, or local permitting requirements for Chula Vista, CA aren't clear.
An independent local plumber can pull the required permits and pressure-test the work before it gets closed up, which is what keeps a finished bathroom from becoming a demolition project two years later. Get connected at (844) 898-0295 before demolition day arrives.