A gurgling drain caused by a blocked plumbing vent
The sound appeared when another fixture discharged, narrowing the problem to pressure imbalance rather than a local trap blockage.
✓Contractor Confirmedrecorded confirmation level
01 / OBSERVED
→Bathroom sink gurgles when the toilet flushes
02 / CONFIRMED CAUSE
→Restricted plumbing vent
03 / REPAIR
→The roof vent obstruction was cleared and the branch was camera-checked.
04 / VERIFY
Fixtures drained silently during repeated simultaneous use.
WHAT CHANGED THE DIRECTION
The evidence that separated the cause
Supporting clues
- Triggered by another fixture
- Trap retained water
- No local slow drain
Checks performed
- Fixture interaction test
- Vent inspection
- Drain camera
Field lessonThe trigger sequence can identify a shared system fault.
