Bathroom drain and supply Lines

[Maint Dog]

1) My house was built in 1996, I’m remodeling a small master bath. I have discovered a 15” pocket behind the wall. The drains and vents are in the center of the pocket, the water supply lines are on opposite walls at opposite ends. The ventilation for both vanities drains are connected to the main vent pipe in the attic. Also the shower supply line in one bathroom is directly across from the sink supply line in the other bathroom.

2) Why would a builder do it this way!?

3) I’m thinking of moving the drains and lines into one wall. Is it against building code for two bathrooms to share the same wet wall?

4) I still have to live in this house; how can I move the plumbing around without disrupting the function of the other bathroom?

 

[hj]

1. Because he wanted to
2. That is the way it is always done when the bathrooms are back to back
3. You can't. You will have to do it in stages.