I am working on a remodeling a kitchen in a single story house with crawl space that was built in the 1950's. I was wondering if there is a better way to plumb the drain lines that are in the attached picture? There is a bathroom sink drain directly behind the wall of the kitchen. The white p-trap is the kitchen drain. I want to remove all the galvanized and replace with PVC, I am assuming that is the correct way to go. The are tied in to the main stack as seen in photo. Any help would be appreciated! Thanks, Joe