Condensation or water droplets forming on the outside of the heater.

Safety first: Ensure electrical parts remain dry. If water is near wiring, turn off power and dry thoroughly.

Steps:

• Differentiate leak vs condensation: Dry the surface completely and observe. If moisture reappears uniformly, it is likely condensation; if from a point, suspect a leak.
• Improve ventilation: Increase airflow in the room or reduce humidity.
• Insulation check: If insulation is damaged or missing in a localized area, have it repaired or replaced.
• Check fittings: Inspect inlet/outlet connections and safety valve for slow leaks and tighten or reseal as needed.