Thanks for all the info!
As for the drain lines, they are actually AC overflow lines that should not have anything flowing unless the main AC drain is clogged. The are usually in a place that would be noticed by the homeowner since it is a sign of bigger problems. That also requires the homeowner to actually do something about it though. If you do any multifamily work it's something to keep an eye out for, especially after summer when the AC's have been running. I have 39 units to clean in one neighborhood.