Rinnai · Water Heater error code

10Air supply or exhaust blockage

Cross-checked Licensed pro only

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Stop: this involves gas or the sealed refrigerant system.

OnCall Tech only describes the symptom. Gas work needs a licensed gas technician, and refrigerant work requires EPA Section 608 certification. If you smell gas: shut off the supply if it is safe, do not switch anything on or off, ventilate, leave the building and call the gas utility.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

Related diagnostic guides

Guide · Water Heater

Water heater leaking: fitting or tank?

The key question is whether the water comes from the plumbing (repairable) or the tank itself (replace the heater). Work from the top down: supply connectors, nipples, T&P valve and its pipe, drain valve, element gaskets. Water from the bottom, under the jacket, or a rusty combustion chamber means the tank has failed.

5 steps ~30 mineasy

Guide · Water Heater

T&P relief valve dripping or discharging

The T&P valve is the tank's last line of defense. It may be failing, or it may be doing its job because the house pressure is too high or thermal expansion has nowhere to go (check valve or PRV on the supply). Diagnose with a pressure gauge; replacement of the valve itself is licensed plumber work in many jurisdictions. Never cap or plug it.

5 steps ~45 minmoderate

Guide · Water Heater

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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