Drain problems
Why does my drain keep clogging?
Updated · Editorial team; not yet technically reviewed
Short answer
A drain keeps clogging when the cause was never removed: buildup still coats the pipe walls after a clog was punched through, something in the pipe (a sag, a broken joint, roots) keeps catching debris, or the drain is receiving grease or wipes it can't carry. Find which one it is before paying for the same fix twice.
Step 1: Notice which drains are affected
One recurring drain points to that fixture's branch line. Several drains, especially the lowest ones in the house, point to the main line or sewer.
The common causes
| Cause | Typical drain | What tells you |
|---|---|---|
| Grease coating the pipe | Kitchen sink | Clogs after heavy cooking; slow draining returns gradually |
| Hair and soap | Shower, tub, bathroom sink | Slow draining; hair visible at the strainer |
| Wipes and paper products | Toilet, main line | Toilet clogs; main line backups |
| Tree roots | Main line / sewer | Seasonal or recurring main line clogs; older clay or cast iron pipe |
| Sag or broken pipe | Main line / sewer | Clogs return within weeks no matter how it's cleaned |
| Venting problem | Any | Gurgling, slow draining with no blockage found, sewer smell |
Fixes that last
- Clean the trap and strainer on a single bathroom drain. It solves most hair clogs.
- Change what goes down the drain. Grease goes in the trash, and only toilet paper goes in the toilet.
- Ask for a camera inspection once a main line has clogged twice in a year. It shows roots, sags and breaks.
- Hydro jetting removes the buildup a snake leaves behind, when the pipe is sound. See hydro jetting.
- Repair the pipe if the camera finds damage. Cleaning a broken pipe only buys time. See sewer line repair.
About chemical drain cleaners
Caustic and acid drain openers can dissolve some hair and soap, but they often don't clear a full blockage. They sit in the pipe, can damage older pipes and finishes, and create a burn hazard for anyone who opens the line afterward. Enzyme products are gentler and work slowly, which makes them suited to prevention rather than clearing a clog. If you've used a chemical opener, tell the plumber before they start.
Common questions
How do I know if the clog is in the main line?
If more than one fixture is affected, or water comes up in a tub, shower or floor drain when you flush or run the washer, suspect the main line and stop using water until it's cleared.
Do garbage disposals cause clogs?
They can. Fibrous and starchy foods, coffee grounds and grease can build up in the kitchen line even after they've been ground.
General information; codes vary by location. See our editorial standards.