One affects a single fixture. The other affects everything in the house at once, and it changes how the job gets done.
A slow bathroom sink and water backing up into the tub when someone flushes the toilet are both "clogged drains," but they are different problems in different parts of the plumbing, and treating them the same way wastes a visit.
A branch line runs from one fixture to the main line. When only one sink, tub or toilet is slow or blocked and everything else in the house drains normally, the clog is in that fixture's branch line, close to where the water went in.
The main line is the single pipe every branch line feeds into before it leaves the house. A blockage there sits downstream of everything, so water backing up shows up somewhere other than where it was sent — flush the toilet and the tub fills, run the washer and the shower drain gurgles.
Water always finds the lowest point it can reach before overflowing. In most houses that is a tub, a shower, or a floor drain in a basement, which is why those fixtures are usually the first sign of a main line problem even though nothing is wrong with them directly.
A drain that gurgles when a different fixture runs is air being pushed back through the trap by water that has nowhere else to go. It is one of the more reliable early signs of a main line issue before it becomes an outright backup.
A branch line clog clears with a light cable through the fixture or a nearby cleanout. A main line needs a heavier cable run from the main cleanout and often a longer reach, because the blockage can be well past where a fixture-drain cable would ever get to.
If a main line has backed up more than once in a short stretch of time, cabling it again without a camera is usually just delaying the same conversation. Roots, a bellied section, or a partial collapse all clear temporarily with a cable and all come back.
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Get a Drain ClearedTell us which drain and how bad — we'll follow up to figure out whether it needs a cable, a jetter, or a camera first.
