Introduction
Hot water pipes running behind walls or ceilings can cause PIR sensors to false-trigger. When hot water flows, the pipe warms up, creating a moving heat source.
Why Water Pipes Cause False Triggers
When someone turns on a hot water tap, hot water flows through the pipes. The pipe rapidly heats up along its length. This moving heat front can be detected by a PIR sensor if the pipe is within its field of view.
Symptoms
- False triggers correlated with hot water usage (showers, dishwashers).
- Triggers occur at specific times of day (morning showers).
- Sensor mounted on a wall with plumbing behind it.
Solutions
- Relocate sensor away from areas with plumbing behind walls.
- Insulate pipes to reduce heat radiation.
- Install reflective insulation barrier between pipes and sensor.
- Use ceiling mounting instead of wall mounting.
- Reduce sensitivity.
Conclusion
Hot water pipes are an unusual but real source of false triggers. Awareness of building plumbing can help you avoid problematic locations.