Symptoms
- Toilet flushes on its own with no one present
- Sensor doesn't respond to hand waves or standing up
- Flush is delayed or inconsistent
- Low battery indicator light, if the model has one
Likely causes
- CommonSensor obstructed or dirtyDust, condensation, or grime on the sensor lens can cause false triggers or missed detections.
- CommonLow batteries or power issueBattery-powered sensor units lose reliability as batteries run low.
- PossibleSensor range miscalibratedSome models have adjustable sensitivity that can drift or be bumped out of range.
- PossibleReflective surfaces nearby confusing the sensorShiny surfaces or moving shadows can trigger false flushes on some models.
What to do
- Wipe the sensor lens gently with a soft, dry cloth to remove dust or condensation.
- Replace the batteries if the unit is battery-powered, even if they seem to have some life left.
- Check the manufacturer's manual for a manual override button, which most models have for exactly this situation.
- Look for a sensitivity or range adjustment dial or setting and reset it to the manufacturer's default.
- Move or cover any reflective or shiny object near the sensor that could be causing false triggers.
- Power-cycle the unit (remove and reinsert batteries, or reset per the manual) if issues continue.
Tools and parts
- Soft cloth
- Replacement batteries
Sensor flush valve batteriesSearch: “toilet automatic flush sensor batteries [type per manual]”
When to call a pro
Call a plumber or the manufacturer's support line if cleaning, new batteries, and recalibration don't resolve it, since the sensor module itself may need replacing.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.