Excellent forum! And thank you in advance for any insights.
I am making plans to add a bathroom to my first floor by utilizing a floor drain in the basement. The current drain, 3-inch, is trapped but not vented, and is approximately 15 feet from the main stack in the house. I intend to remove the trap, install a 3-inch PVC going up-stairs to feed the new bathroom, which will be vented, etc from there. I would like to install a new floor drain in the basement, tying into the 3 inch line using a wye. Question: does the floor drain need to be vented? Iím thinking: yes, or the rush of water in the 3-inch line from the bathroom upstairs would siphon out the floor drain trap. But Iím also thinking no: that a 3-inch line is large enough so this wonít happen. If it is vented, what would be general practice: to use an AAV or to have a vent head up through the floor into the bathroom, where it would tie into the bathroom vents and ultimately go through the roof. That would mean another hole in the floor, not impossible, but not great either.
Block diagram is attached as a pdf.
Thanks for any info.