I own a single story home that is built out of cinder blocks. I haven't owned the home too long, and recently discovered that none of the plumbing is vented. I only have a kitchen and bath sink and bath tub but they all drain into the main sewage line. So I am wondering how or if I can add any kind of venting to my home. I am aware of AAV's, but can I use these for the main sewage line too?