Overview
- Recent reports highlight that repeatedly boiling the same water concentrates dissolved substances such as nitrates, arsenic and calcium compounds, which can degrade water quality over time.
- Microbiologists note that a standard kettle reaching boiling temperatures inactivates common microbes, but variable‑temperature models may not heat high enough to reliably disinfect leftover water.
- The BfR advises discarding water that has stood in pipes or containers, extending this caution to kettles, particularly for immunocompromised people, pregnant women, seniors and small children.
- Consumer groups recommend filling only the amount needed, emptying leftover water and descaling regularly to protect taste, efficiency and device longevity, with the cost of discarding small leftovers estimated as negligible.
- Context from German regulators indicates tap water is tightly monitored, with nitrate limit exceedances now rare and stricter contaminant limits in place under the updated drinking water rules.