Heater operates normally but causes noticeable vibration in nearby plumbing or structure.

Safety: Turn off power before tightening hardware; turn off pump before adjusting plumbing supports.

Steps:

• Tighten mounts: Check that the heater is level and all mounting screws and cabinet fasteners are tight.
• Support piping: Add or adjust pipe hangers and supports to reduce flexing and resonance.
• Adjust pump speed: If using a variable-speed pump, slightly reduce speed to see if vibration decreases.

Persistent vibration from the blower may indicate an imbalanced wheel and require blower replacement.