Drain blockage vs vent obstruction
Flow restriction and pressure imbalance overlap but affect fixtures differently.
↳Partial drain blockage
VS⇧Drain vent obstruction
Typical location
One fixture branch or shared drain line
Shared drain system and roof vent path
Timing fingerprint
During high flow or after repeated use
When another fixture drains or a toilet flushes
Visible or audible pattern
Slow drainage, gurgling and water-level changes
Gurgling, trap movement and possible sewer odor
Best separating check
Compare flow and reactions across connected fixtures
Observe fixture interaction and have vent route assessed
Evidence that weakens it
Normal flow with only wind-related noise
One slow fixture with no interaction
The rule
Use this comparison in Clue Engine →Do not repair the resemblance. Verify the pathway.
Color and shape can overlap. Timing, location and a repeatable check usually carry more diagnostic weight.
