A gurgling drain is caused by air being forced through the water in the trap, which usually means a partial clog or a blocked plumbing vent. If one drain gurgles, the clog is probably in that drain line. If toilets gurgle when other fixtures drain, or several drains gurgle at once, the main sewer line or the vent stack is likely blocked.
Reviewed by Ron Olsen, Master Plumber, certified in Washington
What Makes Drains Gurgle
- Partial clog
- Buildup slows the water down, so air gets pushed back up through the trap.
- Blocked vent
- Leaves, nests or ice in the roof vent stop air from entering the system.
- Main sewer line problem
- A clog, roots or a sag in the main line makes several fixtures gurgle.
- Improper venting
- Drains installed without proper venting can siphon their traps dry.
What You Can Safely Check
- Note which drains gurgle and when it happens.
- Clean the stopper and trap on the affected fixture.
- Plunge a single gurgling sink or tub.
- Check whether the drain also smells. A dry trap or a failed vent can let sewer gas in.
When to Call a Plumber
Call a plumber if more than one fixture gurgles, if toilets gurgle when other drains run, if you notice sewer odors, or if the gurgling comes with slow drains. Clearing roof vents also means working at height.
The repair is usually part of drain cleaning, which explains what the plumber does and what affects the cost.
Tree Roots in Sewer Lines by City
What our city pages say about tree roots in sewer lines:
- Tacoma, WA: Old clay and concrete side sewers under mature trees crack and fill with roots, causing backups.
- Decatur, GA: Large trees send roots into old clay and cast iron sewer lines.
- Chico, CA: Roots from large street and yard trees enter joints in older sewer pipe.
- Montgomery, AL: Old clay sewer lines under mature trees crack and fill with roots.
- Longview, TX: Pine and oak roots enter joints in older clay and cast iron pipe.
- Chattanooga, TN: Clay sewer lines under mature trees crack and fill with roots.
- Portland, OR: Mature street trees and older clay sewer lines lead to root intrusion and recurring clogs.
- Jackson, MS: Old clay sewer lines under mature trees crack and fill with roots.
Other Drain Cleaning Problems
Gurgling Drain Questions
Is a gurgling toilet serious?
It can be. If it gurgles when the shower or washing machine drains, there may be a blockage in the main line, which can lead to a backup.
Can a blocked vent cause a smell?
Yes. A blocked vent can siphon water out of the traps, which lets sewer gas into the house.