Why does Sonic sometimes show a higher water temperature than expected?

You might notice that Sonic reports a water temperature that seems higher than the actual temperature at the tap. This is normal and usually caused by one or both of the following:

1. Heat from nearby hot water pipes

In many homes, the Sonic device is installed on the cold water pipe—which often runs close to hot water pipes. When no water has been used for a while, heat from the hot pipe can radiate into the cold one. This can slightly warm the water in the pipe, leading to an elevated temperature reading.
Once you open a tap or use some water, cooler water from the mains flows through, and the temperature reading typically drops.

2. Sonic’s internal heat

Sonic, like most electronic devices, produces a small amount of heat during operation. Since the temperature sensor is located inside the device itself, this internal warmth can slightly influence readings—especially when the water has been stagnant for a while and no fresh flow has occurred.