I currently have a house in South Carolina with a slab foundation. I am going to replace my tub/surround soon. My house was built in the 1980s. Is it common for the tub drain/overflow pipe to be slabbed into the concrete or a acess left open for future repair/replacement? I've looked everywhere online and can't find this info. I guess they are called box outs, is it code or common to have one?