How the Diagnostic Logic Works
The checker uses a published rule set to compare symptom patterns; it does not claim a confirmed diagnosis.
The tool scores five problem zones: local fixture/trap, shared branch drain, main drain/sewer lateral, venting, and septic/onsite wastewater.
What the engine uses
- Scope: one fixture, one area, several areas, or whole home.
- Trigger: same fixture, toilet, shower, washer, multiple fixtures, rain, or random.
- Cross-fixture reaction: which fixtures respond to another fixture’s discharge.
- Lowest-drain behavior: whether a low floor drain or fixture reacts first.
- Recurrence: whether the issue returned after prior clearing.
- System type: public sewer, septic, or unknown.
No invented confidence percentages
The output labels are Strong pattern, Moderate pattern, and Lower pattern. They are based on absolute rule evidence, not on whichever zone happens to score highest. Strong requires a high score plus more than one independent matched reason. If the answers are too weak to narrow the location, the checker returns an inconclusive result instead of manufacturing confidence.
What the engine cannot know
Without physical access, a symptom tool cannot confirm roots, grease, wipes, pipe collapse, offsets, a belly, corrosion, or ownership of the failed segment. Those require inspection, and often camera work.
Open rules
The rule file is intentionally human-readable at /data/drain-rules.json. The labels are deterministic outputs from those rules; they are not measured probabilities.