Over the past two weeks, a lot of progress has been made on the guest house bathroom. Most noticeably, the door between the living room in the guest house and the bathroom was put in, which involved cutting through the wall to create the rough opening for the door. Also, I built a methane vent that vents any gasses that build up in the drains to the septic tank, preventing them from coming up through the flor drains in the utility room or the shower drain. Finally, the drain lines for the various fixtures were installed.
For the methane vent, I used 4″ PVC and cut through the outer wall with a multi-tool: