Noritz · Water Heater error code

16Outlet temperature spike (often scale)

Cross-checked High-voltage / caution

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Related diagnostic guides

Guide · Water Heater

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Scale insulates the heat exchanger, causing overheat codes and fluctuating temperature. Flush with a pump and descaling solution through the isolation valves.

5 steps ~75 mineasy

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Tankless: error code, no ignition at low flow, or temperature swings

Many tankless complaints are water-side: flow below the activation threshold, a clogged inlet screen, low-flow aerators, or scale in the heat exchanger. Gas supply, venting and combustion codes are blocked: diagnose and refer. Read the code first, then work the water side.

6 steps ~90 minmoderate

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Water heater noisy: popping, rumbling, crackling, humming

Rumbling and popping are usually sediment and scale at the bottom of the tank (gas) or on the elements (electric). They rarely mean the tank is failing but they cut efficiency. Banging or squealing can also come from high pressure and thermal expansion, so check pressure before blaming sediment.

5 steps ~60 mineasy