Rinnai Code 11: No Ignition Fix for Tankless Heaters

Quick Answer

Rinnai Code 11 means ignition failed after 3 consecutive attempts with no flame detected. The most common cause is a dirty flame rod coated with oxide buildup, which prevents the rod from sensing ignition. Other causes include low or interrupted gas supply, worn spark igniter with incorrect gap, and gas valve solenoid failure.

In my fifteen years of servicing Rinnai units, Code 11 is the most frequent call I get. It usually happens during the coldest months when gas pressure fluctuates or after long periods of inactivity. While it sounds serious, most homeowners can resolve this by inspecting the intake and cleaning the internal sensors before calling a professional technician.

RinnaiWaterheaterSeverity: highDifficulty: intermediate78% DIY Success

Time to Fix

20–90 min

Difficulty

intermediate

Parts Cost

$12 – $280

Tools Needed

Phillips #2 screwdriver, Flathead screwdriver

What Does the 11 Code Mean?

Think of this error as a safety lockout. Your Rinnai tried to start its fire three times and failed, so it shut down to prevent raw gas from entering your home. I often find this happens after a gas line has been worked on or if the unit has been sitting idle for a long season.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Flame rod coated with oxide buildup preventing flame detection40%

Gas supply valve partially closed or gas meter issue24%

Spark igniter gap out of specification (should be 3 to 4mm)14%

Wiring connection to flame rod or igniter corroded12%

Gas valve solenoid coil failure10%

Symptoms You May Notice

Code 11 on controller display
Clicking ignition sound followed by unit shutdown
No hot water despite demand
Unit cycles on and off rapidly without heating
Faint gas smell near burner during ignition attempt

Can you reset a Rinnai waterheater to clear the 11 code?

To clear the lockout, press the On/Off button on your controller twice. I recommend waiting about thirty seconds between the off and on press to let the control board fully discharge. If the code pops back up immediately when you turn a tap on, you haven't fixed the physical cause yet.

Tools Required for Diagnosis

Phillips #2 screwdriverFlathead screwdriverFine steel wool or 400-grit emery clothDigital multimeterFeeler gauges or digital caliperFlashlight or headlamp

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

ComponentComponent Under Test

Expected Range30–80 ohms

ConditionIf Open (OL) or infinite, replace component.

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
Flame Rod (Flame Sensor)100074985 · $12–$25	100074985	$12 – $25
Spark Igniter AssemblyContact Rinnai with model number · $20–$35	Contact Rinnai with model number	$20 – $35
Gas Valve AssemblyContact Rinnai with model number · $150–$280	Contact Rinnai with model number	$150 – $280

Frequently Asked Questions

How do I clean the flame rod on a Rinnai water heater?

Shut off the gas and power first, seriously don't skip that part. Once you open the burner cover you'll see a small metal probe with one wire attached. Pull the wire off, remove the single screw holding it in, and take the rod out. Use fine steel wool or a Scotch-Brite pad to polish it until the white oxidation is completely gone and it looks shiny. Don't use a heavy file or you'll remove too much material and damage the rod. Slide it back in, tighten the screw, reconnect the wire. This is probably the most common fix I do in the field on these units.

Why does Rinnai Code 11 keep coming back after I reset it?

A reset just clears the memory, it doesn't fix the underlying hardware problem. If the code comes right back, the control board still can't verify a flame exists. Usually that means gas pressure is too low to sustain combustion, or the flame rod is dirty enough that it can't send a signal back to the board even when there is a flame. On older units I'll often find the wiring harness has corroded right at the connector near the burner, which causes intermittent signal loss that's really frustrating to track down.

What is the difference between Rinnai Code 11 and Code 12?

I explain it like this to customers. Code 11 means the burner never lit at all, zero ignition, no flame detected on any of the three attempts. Code 12 means it did light successfully but then went out mid-operation while you were in the shower. Code 12 is usually a venting issue or a gas regulator that can't keep up with demand once the heater's running at full capacity. Two different problems even though they kind of feel the same from your end, which is standing there with cold water running over you.

Can I replace the Rinnai flame rod myself?

Yeah, honestly it's one of the easier repairs on these units. You need a Phillips screwdriver and maybe fifteen minutes. Since you're not breaking into any sealed gas lines, the risk is pretty low as long as power and gas are completely off before you start. Part number 100074985 fits a lot of the common Rinnai models. Just don't drop the mounting screw into the bottom of the cabinet because those things are a real pain to fish out. Ask me how I know.

My Rinnai is only 2 years old. Why is it showing Code 11?

On newer units I almost always look at external factors first. If you've got a propane tank, check the level. LP systems will trigger Code 11 before the tank's even visually empty because pressure drops as the tank gets low. If you're on natural gas, check if the city was doing any line work nearby, because air pockets in the pipes after that kind of work can prevent ignition for a while. A two-year-old flame rod rarely fails on its own unless your intake air is really dusty or you're near the coast where salt air speeds up corrosion.

How much does it cost to fix Rinnai Code 11?

Depends entirely on what's actually broken. If it's just a dirty flame rod, cleaning costs you nothing but an hour of your time. The flame rod itself runs about $15 to $25 online, part 100074985. An igniter assembly is $40 to $80 depending on the model. If the gas valve solenoid's gone, you're looking at $150 to $300 for the part alone. A service call to have a tech come diagnose it usually runs $100 to $200 just to show up, so it's worth trying the DIY cleaning steps first before you pick up the phone.

Related Rinnai Waterheater Error Codes

Code: HUBRinnai Tankless Water Heater Error Codes: Complete Guide Code: 12Rinnai Code 12: Flame Failure During Operation Code: 10Rinnai Code 10: No Gas Supply or Gas Valve Failure Code: RESETHow to Reset a Rinnai Tankless Water Heater: All Models Guide

Same Fix on Other Brands

Navien waterheaterE003: Navien E003 Error Code: Ignition Failure Fix for NPE and NCB Series

Models Known to Experience 11 Errors

This repair applies to most Rinnai waterheaters with this error code. Common model numbers include:

RUR98iN, RU199iN, RU98eN, V65iN, RL75iN, RU160iP

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 14, 2026