Rinnai LC Code — What It Means and How We Fix It in Los Angeles

May 14, 2026  |  Troubleshooting

The Rinnai LC code is the single most common Rinnai-related service call we receive in Los Angeles. If you're seeing LC flashing on your Rinnai display, here's exactly what's happening and what you need to do.

What Does Rinnai LC Code Mean?

The LC code on a Rinnai tankless water heater stands for Lime and scale Code. Unlike fault codes (11, 12, 14 etc.) that indicate something has failed, LC is a maintenance reminder — it's telling you the heat exchanger needs descaling.

Rinnai calculates this based on operating hours and incoming water temperature. In Los Angeles, where water hardness is very high, the LC code typically appears every 12–24 months.

Can You Clear the LC Code Yourself?

Technically yes — you can reset the LC counter from the controller. But clearing the code without actually descaling the unit is like resetting your car's oil change light without changing the oil. The scale is still there, still restricting flow, still causing the heat exchanger to work harder than it should.

If you've been resetting the LC code without descaling, your heat exchanger has likely accumulated significant scale damage. The longer this continues, the higher the risk of a permanent code 14 (thermal fuse failure from overheating) or heat exchanger failure.

What Happens If You Ignore the LC Code

Scale buildup progresses in stages:

1. LC code appears: Light scale. A descaling flush clears it completely.
2. Code 14 (thermal fuse): Moderate scale has caused overheating. Thermal fuse needs replacement in addition to descaling.
3. Code 61 (combustion fan): Scale and overheating have stressed the fan motor. More expensive repair.
4. Heat exchanger failure: The exchanger cracks or corrodes through. At this point, the repair cost often exceeds the value of the unit.

How We Descale a Rinnai in Los Angeles

Our descaling process:

1. Isolate the unit and connect a descaling pump to the service ports
2. Circulate food-grade white vinegar or commercial descaling solution through the heat exchanger for 45–90 minutes
3. Flush the system thoroughly with clean water
4. Reset the LC counter from the Rinnai controller
5. Test flow rate and temperature output to confirm the unit is performing correctly

The entire process takes about 1.5–2 hours. Call Simple Water Heater & Filtration for Rinnai descaling service throughout Los Angeles and the San Fernando Valley.