You can determine that your tankless water heater requires an immediate descaling flush if you notice a noticeable drop in hot water temperature, longer delays before hot water arrives at taps, strange rumbling or banging noises from boiling scale inside the heat exchanger, or recurring error codes related to high temperature limits. Hard water minerals insulate the heat exchanger coils, forcing the unit to work harder. Verification: Flush the heat exchanger using a vinegar descaling kit and inspect the drained solution for white calcium scale debris.
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