Rinnai tankless water heater repair in San Jose
A Rinnai that stops heating usually tells you why on its display. The code narrows the problem down; the repair still needs someone to test the gas, venting, sensors and scale behind it.
- 24/7 answered
- Phelan Ave San Jose office
- Tank, tankless, heat pump
Perfect Tankless Plumbing, San Jose, CA
Rinnai tankless repair in San Jose starts with the code on the display: 10 points to air supply or exhaust, 11 to ignition, 12 to flame failure, 14 and 16 to overheating, 79 to a leak inside the unit and LC to scale; we test the cause behind the code, repair or descale the unit, and confirm it runs at full fire.
Updated September 2026
Water Heaters
What a Rinnai code tells you, and what it does not
Rinnai units report faults as two-digit codes, with a few letter codes such as LC. The code says what the unit detected, not always why. Code 11, for example, means the burner did not light, which can come from a closed gas valve, low gas pressure, a dirty flame rod or a failed igniter.
We are an independent plumbing company, not affiliated with Rinnai, and we work on Rinnai units of all ages. We read the code history where the model stores it, test the likely causes in order and fix the one that is actually failing.
Warning signs
Common Rinnai codes and what they point to
- Code 10Air supply or exhaust blockage.
- Code 11No ignition.
- Code 12Flame lost during operation.
- Codes 14 and 16Overheat protection.
- Code 79Water leak inside the unit.
- LC codesScale in the heat exchanger.
Ignition and flame codes
Codes 11 and 12 are the ignition and flame failures: 11 means the burner did not light, and 12 means it lit and then lost the flame. We start with the simple causes, a partly closed gas valve, low gas pressure when other appliances run, or a power interruption, then move to the flame rod, igniter and gas valve inside the unit. Loose or dirty flame rods and electrodes are a common cause of both codes, and cleaning or replacing them often brings the unit back without bigger parts.
Scale and overheat codes
The LC codes mean scale is building up in the heat exchanger, and in hard-water parts of the valley they are among the most common Rinnai calls. Scale also drives overheat codes 14 and 16, because a coated heat exchanger runs hot. The fix is a full descaling flush with a pump and descaling solution through the service valves, followed by cleaning the inlet filter. If the unit has no isolation valves, we fit them so future flushes are quick.
Venting, leaks and board faults
Code 10 means the air supply or exhaust is blocked, from a nest in the vent terminal, a crushed vent, or a condensate line backing up into a condensing model. Code 79 means the unit has detected water inside the cabinet, so we shut off the water and gas and find the leaking fitting or heat exchanger before anything else. Faults that remain after the causes are cleared point to a sensor or the control board, which we test before replacing.
How the job runs
How a Rinnai repair runs
- 1
Read the code
And the stored code history.
- 2
Check the simple causes
Gas, power, filter, vent.
- 3
Test the components
Flame rod, igniter, sensors.
- 4
Repair or descale
Fix the cause, not the code.
- 5
Run at full fire
Gas pressure and temperature.
- 6
Set a flush schedule
Matched to your water.
Local context
Why scale codes come up so often here
Hardness depends on which supply reaches the tap. In Sunnyvale, city well water averaged about 290 mg/L of hardness, against about 111 mg/L for Valley Water and 57 mg/L for SFPUC water. A Rinnai on well-heavy supply builds scale far faster than one on imported water, which is why we ask where you live before deciding how often your unit needs descaling.
DIY or call
What you can check before calling
| Task | Reasonable to DIY | Call a plumber |
|---|---|---|
| Gas valve open | Yes | Code returns |
| Power and breaker | Yes | No display at all |
| Inlet water filter | Yes, if accessible | Filter damaged |
| Vent terminal outside | Look only | Anything blocking it |
| Descaling flush | Some owners | LC returns quickly |
| Inside the cabinet | No | Always |
Cost factors
What a Rinnai repair costs depend on
We do not publish a local repair price; the code, the cause and the part set the cost.
- Cause behind the code. a valve or a component
- Descaling. a flush versus a part
- Parts. flame rod, igniter, sensor or board
- Venting. a blockage or a damaged section
- Isolation valves. fitted if missing
- After-hours timing. emergency visits typically cost more
FAQ
Rinnai Tankless Water Heater Repair questions from San Jose homeowners
You can often clear it temporarily, but the scale is still there. Flush the unit soon to avoid damage.
No ignition. Check that the gas is on, then call if it returns.
Yes. It means water inside the unit. Shut off the water and gas and call.
Yes, as long as parts are available. If not, we'll tell you plainly.
We're an independent plumbing company that repairs Rinnai units, not affiliated with Rinnai.
Same family
Related work in water heaters
Recirculation Pump Installation
Dedicated return line, Under-sink crossover.
Dedicated return line and related workTankless Descaling and Flush
Isolation valve retrofit, Inlet filter cleaning.
How we handle tankless descaling and flushHeat Pump Water Heater Installation
Hybrid 240V units, Condensate and clearance planning.
Hybrid 240V units and related workTankless Water Heater Replacement
Like-for-like swap, Upsizing a tired unit.
How we handle tankless water heater replacementTankless Water Heater Installation
Gas tankless, Electric tankless.
How we handle tankless water heater installation
From our guides: Rinnai Error Codes Explained: 10, 11, 12, 16, 79 and LC.
One number, any hour
Get your Rinnai heating again
Call and read us the code on the display. It helps us bring the right parts.
