Rinnai Tankless Error Codes: What They Mean & What to Do
Your Rinnai is showing a number or letters on the display. Here’s what each code means and what to do next.
Updated October 2026 · By the Hot Water Heater Factory team
Rinnai error codes and what they mean
| Code | What it means | What to do |
|---|---|---|
| 03 | Power interruption during bath fill | Turn off the hot water taps, then press the ON/OFF button twice. |
| 10 | Air supply or exhaust blockage | Check the outside vent for leaves, nests or anything blocking it, then text us. |
| 11 | No ignition | Make sure the gas is on (and the propane tank isn’t empty), then text us. |
| 12 | Flame failure | Often low gas supply or a venting problem. Text us the code. |
| 14 | Thermal fuse (overheat safety) | Don’t keep resetting it. A technician needs to check this. Text us the code. |
| 16 | Over temperature warning | Often scale buildup. The unit may need descaling. |
| 25 | Condensate trap error (condensing models) | Check that the condensate drain line isn’t kinked or blocked, then text us. |
| 31 | Burner sensor error | A technician needs to check this. Text us the code. |
| 32 | Outgoing water temperature sensor fault | A technician needs to check this. Text us the code. |
| 33 | Heat exchanger outgoing temperature sensor fault | A technician needs to check this. Text us the code. |
| 52 | Modulating solenoid valve signal abnormal | A technician needs to check this. Text us the code. |
| 61 | Combustion fan failure | A technician needs to check this. Text us the code. |
| 65 | Water flow control fault | A technician needs to check this. Text us the code. |
| 70 | Sensor harness connection | A technician needs to check this. Text us the code. |
| 71 | Solenoid valve circuit fault | A technician needs to check this. Text us the code. |
| 72 | Flame sensing device fault | Often a dirty flame sensor. A technician needs to check this. Text us the code. |
| 73 | Burner sensor circuit error | A technician needs to check this. Text us the code. |
| LC | Scale buildup in the heat exchanger | The unit needs descaling. See tankless descaling. |
| No code | Nothing happens when hot water is turned on | Open the hot tap all the way and check that the controller is on. If it still won’t start, text us. |
Code meanings come from Rinnai’s technical documentation. Codes and remedies can vary by model, so check your owner’s manual too.
What should I do when my Rinnai shows a code?
- Write down the code. If it shows more than one, note each one.
- Turn off the hot water taps. Some codes clear when the unit is turned off and back on, but if the code comes back, the unit is telling you something.
- Don’t keep resetting codes for overheating, flame or gas problems.
- Text us the code and a photo of the label. We’ll tell you what it likely means and bring the right parts.
Other brands: Navien codes · Noritz codes · Takagi codes. Many codes come from scale buildup; see tankless descaling and maintenance.
Questions we hear a lot
What does code 11 mean on a Rinnai tankless?
No ignition. The unit tried to light and couldn’t. The most common causes are the gas being off, an empty propane tank, air in the gas line after other work, or an ignition part. Check that the gas is on, then text us.
What does LC mean on a Rinnai?
Scale buildup in the heat exchanger. The unit needs to be descaled. In hard Inland Empire water, most tankless water heaters need it about once a year.
Can I reset a Rinnai error code?
Turning the unit off and on clears some codes. If the same code comes back, or it’s an overheating or flame code, have it checked rather than resetting it again.
Rinnai showing a code? Text us now.
Send a photo of your water heater’s label and tell us what’s happening. A real person texts you back.