Not every noise is a problem. Here is what manufacturers say each one usually means.
| Noise | Usual cause | What to do |
|---|---|---|
| Popping or rumbling | Sediment in a tank heater | Flush the tank |
| Ticking | Heat traps or pipes expanding | Normal |
| Sizzling | Water hitting the burner or elements, possibly a leak | Turn off and have it inspected |
| Whining or screeching | Restricted flow, a partly closed valve, or a relief valve issue | Open valves fully; call a pro |
| Hissing | A possible leak | Turn off and call a pro |
Electric heaters
A.O. Smith lists scale buildup on the heating elements as a cause of noise in electric heaters; the fix is having the elements cleaned or replaced. It also notes that expansion and contraction noises are not necessarily harmful.
General information, not professional or legal advice; follow your manufacturer's manual, and your installer and local permit office have the final word. Sources:Rheem, Water heater noises guide; A.O. Smith, Water heater making a noise; A.O. Smith residential electric water heater manual (185762).
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