A one-time clog is normal. Hair, soap scum, food — they accumulate and eventually choke the line. A plunger or a small auger clears them, and the drain stays clear for years. When the same drain backs up every few months, something deeper is wrong.
Five reasons drains clog repeatedly
1. The line has a belly
Drain lines are supposed to slope a quarter inch per foot. Soil settles, joints sag, and sections develop low spots ("bellies") that hold water and debris instead of moving them along. Hair and grease catch in the belly and grow into a clog every few months. Only a camera inspection confirms it.
2. Old galvanized or cast iron pipe is corroding from the inside
Galvanized drain lines from the 1960s and earlier corrode internally. The inside diameter narrows from 2 inches to under an inch, and rough rust deposits catch every scrap of anything that goes down. No amount of snaking fixes it — the pipe itself has to be replaced.
3. Tree roots in the main line
Roots find any joint or crack and grow into the warm, nutrient-rich line. A snake clears them temporarily, but they re-grow in 6–18 months. The fix is hydro jetting and, if the joint is damaged, a spot repair or pipe lining. Read more on roots →
4. The vent stack is blocked
Every drain system needs air to flow properly. The vent stack — that pipe poking out of your roof — provides it. If it's blocked by leaves, a bird's nest, or ice, drains gurgle and run slow even when the pipe itself is clean. A telltale sign: water in one fixture causes another to bubble.
5. Habit, not hardware
Sometimes the line is fine and the household is the issue. Long hair down the shower with no strainer, grease and coffee grounds down the kitchen, "flushable" wipes (they aren't) in the toilet. A few habit changes and inexpensive screens often fix the problem entirely.
How to diagnose what you're dealing with
- One fixture clogs: the trap or branch line. Local fix.
- Multiple fixtures clog: the main line. Camera and possibly hydro jet.
- Toilet bubbles when the washer drains: main line restriction or vent issue.
- Backup happens after heavy rain: sewer line is compromised — groundwater is getting in.
- Smell of sewage from a drain that's clear: dry trap or broken vent.
When to stop snaking and call
If a drain clogs more than twice in a year, snaking is treating the symptom. Get a camera down the line. A 30-minute inspection tells you exactly what's wrong, where, and what the real fix costs. We do free camera inspections with every main-line cleaning.