I guess it depends on what you are looking to clear in the way of a clog. Acid (vinegar) can attack the metal of the pipe. But the problem is that it would never touch the pipe…at least not in the house. Maybe farther down the line to the sewer. But to be honest acetic acid (vinegar) is a very mild acid and would likely not do much damage to the pipes. But it may not do much for the clog either. What goes down your drain that you believe is clogging the pipes? If it is organic matter (hair, fats, etc) you are probably not putting the right product down the pipes. Bases work much better than acids for this application. That is why Drano works for it. Acid is good for removing calcium deposits and things like that (iron deposits, e.g.) But caustic helps dissolve organic matter better. So if you are trying to clean calcium or iron deposits off the pipes, the vinegar will do great. Other than that, I’d go with Drano.