While Rinnai hot water heaters are exceptionally reliable, they can experience a few standard operational issues over time, primarily related to water quality and venting. The most frequent problem is mineral scale buildup on the internal heat exchanger coils, which restricts water flow, reduces heating efficiency, and triggers error codes if annual descaling is neglected. Other common issues include flame-sensing rod degradation, igniter wear, blocked intake or exhaust venting, and error codes triggered by low incoming gas pressure.
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