Dryer Vent Cleaning & Inspection in Belmont, CA

## D80 Warning and Flow Sensor Faults on a Nearly New LG Dryer When a Belmont homeowner contacted us about their LG DLEX7900WE dryer repeatedly flashing D80 and flow sensor warning lights, the appliance itself was not the problem. On LG units, the D80 code indicates that the exhaust duct is approximately 80% blocked, and the flow sensor fault confirms that the dryer's internal sensor is detecting critically low exhaust airflow. Even on a fairly new dryer, a restricted vent system will trigger these warnings immediately. Our first step was to pull the unit away from the brick wall and assess the full duct run before any cleaning began. ## What We Found: Severe Lint Buildup and a Marginal Duct Run The before photos tell a clear story. The exterior termination cap on the brick wall was heavily packed with compacted lint across its louvers, nearly eliminating airflow at the outlet. The interior garage duct run, approximately 13 feet long with a 90-degree elbow, a 60-degree elbow, and a 45-degree elbow, was coated with lint accumulation along its entire length. The existing semi-rigid transition duct showed foil-tape repairs and improper joint orientation, meaning the joints were running in the wrong direction and allowing lint to catch and accumulate at every seam. Per IRC M1502.1, the dryer exhaust system must be installed to match manufacturer specifications, and the combination of improperly oriented joints and a heavily fouled termination cap put this installation well outside those requirements. The duct interior was occluded well beyond the 50% threshold associated with severe lint buildup (issue code: LINT_BUILDUP_SEVERE), a condition that creates serious fire risk and the exact back-pressure that drives D80 fault codes. ## What We Did: Full Cleaning and Transition Duct Replacement We disconnected the transition duct, cleaned the entire 13-foot main duct run using rotary brush equipment, and cleared the exterior termination cap of all lint and debris. The improperly installed semi-rigid transition duct was removed and replaced with a new Innova flexible dryer duct, properly oriented at every joint so that seams shed lint rather than collect it. The exterior vent cap was cleaned and inspected to confirm the backdraft damper opens and closes freely, as required by IRC M1502.3. After returning the dryer to its operating position and reconnecting the exhaust system, the unit was powered up and the D80 and flow sensor warnings were fully cleared. The after photos show the duct area clean, properly connected, and free of the debris accumulation visible before service. ## Outcome and Recommendations With the duct cleaned and the transition duct replaced, airflow at the termination was restored to a level that satisfies the LG DLEX7900WE's exhaust requirements and eliminates the conditions that triggered the fault codes. Homeowners in Belmont with similar garage or laundry-room installations should note that multi-elbow duct runs, even at modest lengths, accumulate lint faster than straight runs because each bend creates turbulence and a surface for fibers to settle. Per the manufacturer's guidance and general best practice under IRC M1502.1, annual professional inspection is recommended for this type of installation to keep the system clear, efficient, and safe.