The idea would be to prevent sewage from backing up into the basement if the main sewer line ever gets clogged (which has happened a couple of times in the past). My thinking is that if I can prevent any backup through the laundry sink drain, then any sewer clogs in the future will just overflow at the curb vent by the street in front of the building -- and will not back up into the basement.
When I do Google searches for sewer backflow preventers, all I see are devices that are for a 4-inch main sewer line. Here's a YouTube video example of one type of 4-inch backflow preventer that I see online:
But that is not what I want or need. All I would really need for this application is a backflow preventer for the laundry sink which has a 2-inch drain line.
Does anyone know of a drain line backflow preventer that is made for a sink drain such as a laundry sink?