How to tell a slow drain from a main line problem

One slow sink is a local clog. Two fixtures backing up at once, or a tub that gurgles when the toilet flushes, points at the main line. The difference matters because a local clog is an hour with a cable machine and a main line problem can mean roots.

Before you call, note which fixtures are affected and whether the lowest drain in the house is the first to back up. That one answer tells the technician which equipment to bring.