Key Takeaways
- Rheem error code 11 means the flame rod did not detect a flame. Rheem's service manual states it as "Flame rod(s) does not detect flame." The unit called for gas, could not confirm the burner lit, and closed the gas valve.
- 11 and A011 are the same fault on two different displays. Legacy remotes print a bare
11. Current condensing RTGH units and the IKONIC S-series printA011on an LCD. Rheem publishes the two troubleshooting paths separately with no crosswalk, which is why searching "A011" turns up so little. - On the legacy `11` generation, indoor and outdoor units get checked differently. Rheem's older tankless troubleshooting manual flags two flame rods on indoor models, wired to connectors M and T. That split matters more than condensing versus non-condensing, and it does not carry over to the current A011 generation, which reads a single flame rod at a different connector.
- Across six years of our own records, code 11 is the tankless code we get called about more than any other, and the fix is usually cleaning the flame rod rather than replacing a component.
- Most of these end inside one visit. A tankless diagnostic in Orange County runs $298 to $377.
You have almost certainly already looked the code up, and you are right about what it points to. So here is the short answer, then the part nobody publishes.
Rheem error code 11 means the unit tried to light and could not confirm a flame. A fan pulls in combustion air, the gas valve opens, the igniter sparks, and a thin metal rod sitting in the burner flame confirms the burner actually lit. When that confirmation does not arrive, the control closes the gas valve and posts the code. Nothing is running with gas flowing and no fire, which is exactly what you want a gas appliance to do.
What people ask next is price, availability, and whether we even work on Rheem. Ballpark: most code 11 calls resolve inside one diagnostic visit at $298 to $377, and we usually have same-week availability. On the Rheem question, Rheem is about 15.2% of the water heaters we photograph on service calls (2,456 data plates across our job history), and we have logged 76 tankless service jobs on Rheem units while installing only a handful ourselves. We service far more Rheem than we sell. Our water heater service page covers that work.
Now the part that matters most, and it takes ten seconds.
First, read the exact string on your remote.
There are two generations of Rheem tankless display code for this fault. Which checklist applies depends on what the remote prints, not on how old you think the unit is.
| What your remote shows | Where you see it | What it means | What the manufacturer checks first |
| `11` on an LED remote | Legacy units, and the current Ruud RUTGH and Richmond Encore RMTGH condensing manuals | Flame rod does not detect flame | Gas shutoff valve fully open, gas supply, venting |
| `A011` on an LCD remote | Current Rheem condensing RTGH models and the IKONIC S-series | "Flame Not Detected From Flame Rod" | Adds the gas filter and the air filter as first-line checks, and renames the PGFR the "gas-air ratio valve" |
If your screen says A011, you are not looking at a different problem. It is the same one on a newer remote, with two extra first-line checks the older checklist never mentioned. Rheem publishes those two checklists in separate documents and prints no crosswalk between them, which is why the A011 string returns so little when you search it. The information exists. It is just filed somewhere a homeowner is unlikely to look.
[SME: VERIFY] The A011 string is confirmed in Rheem's current IKONIC RTGH service manual, and the bare 11 is confirmed in the older tankless troubleshooting manual. What is still open is the boundary: A011 appears nowhere in the 2024 Rheem-authored manual shared by Ruud RUTGH and Richmond Encore RMTGH, which prints a bare 11. The table routes on what the reader's screen shows, which holds either way, but "Where you see it" needs one word changed if the boundary turns out to be model-based rather than remote-based.
On older units, indoor or outdoor changes what a technician looks for.
Most write-ups split Rheem tankless units by condensing versus non-condensing. On the legacy 11 generation the published diagnostic path actually splits on indoor versus outdoor.
Rheem's older tankless troubleshooting manual walks the flame rod check through a white connector marked M and a blue connector marked T on the control board, and notes alongside the diagram that indoor models carry two flame rods. Two rods means two places the confirmation can come up short, so an indoor unit in a hallway closet and an outdoor unit on the side of the house can show the identical code and get checked two different ways.
Worth knowing that this does not carry forward. On the current A011 generation the flame rod is read through a single connector, and the M and T pair is not part of that unit's procedure. It is a good example of why the string on your remote is the thing to go by rather than a chart written for a different generation.
What people assume, and what it usually turns out to be.
Almost everyone who reads up on this code arrives with a theory, usually the igniter, the gas valve, or the control board. Those are real causes. They are just not the common ones.
Across six years of our own service history, code 11 is the tankless error code we are called about more than any other: 97 jobs and 24 tracked calls. The most common thing our technicians do on those calls is sand the flame rod or the ignition rod. Deposits build a thin insulating layer, the confirmation signal drops below what the control expects, and the unit stops trusting a flame that is genuinely there. A few passes with fine abrasive restores it. Worth knowing before anyone quotes you a part.
Here is what we find, roughly in order of frequency.
Deposits on the flame rod. The number one cause by a wide margin. Orange County water runs roughly 8 to 19 grains per gallon depending on your district, and scale is the dominant local factor across the whole tankless category.
Gas supply that is not fully there. A shutoff valve someone closed during a remodel and never reopened. A tripped earthquake safety valve at the meter, which trips from delivery trucks and construction, not just earthquakes. Or a meter that cannot keep up when the furnace, dryer and pool heater all run at once. Rheem's own first check on the legacy code is the gas shutoff being fully open, and that is not an accident. Pressure testing belongs to a licensed plumber with a manometer, and it touches your gas line system.
A clogged gas filter or air filter. The A011 generation's addition, and a useful one. The newer checklist puts both filters ahead of component diagnostics.
Air and venting. When the vent run is restricted, exhaust cannot clear the way it should, and the oxygen and combustion gas mixture in the chamber stops supporting a stable flame. Fire needs oxygen. Correcting the venting corrects the code. We see this most on horizontal terminations, where the vent exits a side wall with no bird block or screen. We have pulled hornet nests and leaf blower debris out of those.
Wiring and grounding. The confirmation circuit needs a complete electrical path. A loose connector at the flame rod, a corroded terminal, or a ground that has come adrift reads the same as no flame at all. Rheem's own first move on this branch is simply to pull the flame rod connectors and reseat them, because a loose connection is common enough to check before anything gets replaced.
The gas-air ratio valve or the control board. Real, and the least common. We rule these out last, because our own numbers say we should.
"No hot water since last night" and the display says 11.
That is how most people describe this, and they usually name a fixture rather than the appliance. It is the shower, or the master bath. Same event. Code 11 means the burner is not confirming, so nothing is heating, so every hot tap in the house runs cold.
Three things are worth trying before you call anyone.
Check the gas. Walk out to the meter. The shutoff handle should be parallel to the pipe, which means open. Look for the earthquake valve, a second valve on the line and usually brass, and reset it if the indicator has tripped closed. Then see whether your stove lights. If nothing gas-powered works, the water heater is not the story.
Look at the vent termination. Check for nests, leaves or debris. Clear what you can see at the opening only, and do not reach into the pipe.
Power cycle once. Off, thirty seconds, back on. If a momentary condition set the code, it clears. If it comes back, something persistent is behind it.
What it costs, honestly.
We price tankless work as a visit rather than as a parts list, so three tiers cover nearly everything.
Cost Breakdown: Rheem code 11 and A011 in Orange County, 2026 pricing. Heat exchanger replacement is absent on purpose. It is genuinely uncommon, and we have not done it enough times to publish an honest range off our own records.
| Tier | What it is | Typical cost |
| 1 | Tankless troubleshooting and diagnostic visit. Most code 11 calls end here | **$298 - $377** |
| 2 | Flame rod cleaning, performed during the visit | $195 - $279 |
| 2 | Ignition rod or flame rod replacement | $200 - $425 |
| 2 | Control board, complete service, usually across two visits | ~$1,200 |
| 2 | Control board install when you already have the part in hand | $525 - $780 |
| 3 | Full unit and installation, when repair is not the right call | **$5,950 - $8,975** |
Tier 1 is where most of this lands. Looking only at how jobs were booked, before any technician saw the unit, a tankless diagnostic visit becomes a full replacement about 5% of the time. Nineteen times out of twenty, we come out for a code and we fix it.
The control board is the one that takes two visits. The part is not on the truck. We call the manufacturer's technical support line, work through their diagnostic, then either pick the board up at will-call or wait for it to ship. That coordination is what puts the all-in figure near $1,200, and it is why it should not be compared to a single line item on an invoice.
[SME: VERIFY] Two pricing questions before publish. Is the $195 to $279 flame rod cleaning in addition to the $298 to $377 diagnostic, or performed inside it? The invoice record suggests inside. And confirm whether the $95 truck and dispatch line that appeared in 2026 is additive, because a reader comparing quotes will notice.
For the wider view, we keep a full breakdown of water heater repair costs.
If another plumber already told you to replace the Rheem.
About a third of the people who first contact us about a water heater already had someone else out and already have a diagnosis in hand. The question is almost always some version of "does this sound right to you, or could the repair be something less?"
It deserves a straight answer rather than a pitch about the other company. Most of the time the other diagnosis is correct about the symptom and simply lands on a different recommendation, and reasonable technicians do land in different places. What we would recommend is confirming the cause before anyone spends replacement money on a code that, in our records, is most often resolved by cleaning a rod.
Two things genuinely move the answer toward replacement. Age is the big one: the tankless units we service average about nine years old with a clear spike at the ten-year mark, and past that point a large component repair starts competing with a new unit on its own merits. The second is a repeat pattern, where a code clears after a cleaning and returns within days.
Our comparison of Noritz, Rinnai and Rheem tankless units covers how the three lines differ, and our tank versus tankless breakdown covers the bigger decision.
What these calls actually look like.
The pattern barely varies. Someone calls with a code on the display and no hot water, and usually with the sense that they have already done the reading and come up short.
We get out there, pull the front cover, and on most of these the rods carry enough deposit that the confirmation signal has dropped below what the control will accept. A few minutes with fine abrasive, reassemble with a fresh gasket, run a full cycle, and it lights. On an older indoor unit that means checking both rods rather than one, because a clean rod at one connector and a coated one at the other reads the same as neither working.
Worth saying out loud: the unit was never the problem in the way people fear. It refused to run gas without proof of flame, and that refusal is why nothing worse happened while they waited for us.
[SME: VERIFY] Eric to confirm this matches what he sees on Rheem specifically, or swap in a real call. Written as a recurring pattern rather than a single episode on purpose.
Keeping a Rheem code 11 from coming back.
Most of what causes this is gradual, which means most of it is preventable.
Descale once a year. The most useful thing you can do for a tankless system in Orange County, and the most common tankless service we perform by a wide margin: 45.1% of all our tankless service jobs. A flush runs $255 to $316, with $316 the current 2026 price. The rods get cleaned during that visit and the scale behind half the list above comes out before it causes anything. A booked flush visit becomes a replacement roughly 0.3% of the time.
Put a bird block or screen on a horizontal termination. If your vent exits a side wall rather than the roof, ask about it at the next service visit. Small item, heads off a whole category of calls.
Watch for the early tell. If the unit takes two or three attempts to light before it catches and then runs fine, that is the confirmation signal drifting down before it crosses the threshold. Cheapest possible moment to deal with it.
An annual plumbing inspection picks this up alongside everything else, and our water heater service page covers what a tankless visit includes.
FAQ.
What does Rheem error code 11 mean?
The flame rod did not detect a flame. Rheem's service manual states the condition as "Flame rod(s) does not detect flame." The unit ran its ignition sequence, could not confirm the burner lit, and closed the gas valve. The most common cause is deposits on the flame rod, followed by gas supply issues and restricted venting.
My Rheem shows A011, not 11. Is that a different code?
No. A011 and 11 are the same fault on two display generations. Legacy remotes print a bare 11, which Rheem's older manual describes as "Flame rod(s) does not detect flame." Current condensing RTGH models and the IKONIC S-series print A011 on an LCD, which Rheem's current manual describes as "Flame Not Detected From Flame Rod." Same event, same component, different document. The A011 path adds the gas filter and the air filter as first-line checks and refers to the PGFR as the gas-air ratio valve. Rheem publishes the two paths separately without a crosswalk, which is why the A011 string returns so little when you search it.
There is no hot water in the shower and the unit shows 11. Same thing?
Yes. Code 11 means the burner is not confirming a flame, so the unit is not heating at all and every hot tap runs cold. People usually describe it by the fixture they noticed it at. The fixture is not the issue.
Can I reset Rheem code 11 myself?
You can try, once. Off, thirty seconds, back on. If a momentary condition triggered the code it clears and stays clear. If it returns, repeated resets will not resolve it. Before resetting, confirm the gas shutoff at the meter is fully open and the earthquake valve has not tripped. Both are quick, and both sit on the manufacturer's own first-check list.
How much does it cost to fix Rheem code 11 in Orange County?
Most are resolved inside a single diagnostic visit at $298 to $377. Flame rod cleaning during that visit runs $195 to $279, and rod replacement runs $200 to $425. A control board is the uncommon high end at around $1,200 all in, usually across two visits because the part is not carried on the truck. Full replacement runs $5,950 to $8,975 and is not where most code 11 calls end up.
Do Ruud and Richmond tankless units use the same code?
Yes. Rheem, Ruud and Richmond are the same manufacturer family and share the code tables. The current Ruud and Richmond owner's manuals are the same Rheem document down to the part number. What varies is what the remote prints, which is why reading the exact string matters more than the badge on the front.
Another plumber said it needs replacing. Is code 11 a replacement situation?
Usually not. In our own booking data a tankless diagnostic visit becomes a full replacement about 5% of the time, and code 11 specifically is most often resolved by cleaning the flame rod. Age changes the math: at ten years and up, a large component repair starts competing with a new unit on its own merits.
The bottom line.
Rheem error code 11, and the `A011` your newer remote prints instead, mean the same thing: the unit called for gas, could not confirm a flame, and shut the gas off. That is the appliance working correctly.
Three things get you most of the way:
- Read the exact string on the remote,
11orA011. It decides which of Rheem's two published checklists applies. - Note whether the unit is indoor or outdoor. On the older generation that decides whether a technician is checking two flame rods or one.
- Start with the cheap causes. Gas fully on at the meter, earthquake valve not tripped, vent termination clear. Then the rods, which is where most of these end.
If you are in Orange County and your Rheem, Ruud or Richmond unit is showing 11 or A011, give us a call at (949) 328-6002 or schedule a visit. We work on these constantly, we usually have same-week availability, and we will tell you which of the three tiers you are in before we start. For the same code on other brands, we have written up Noritz code 11 in depth, and Rinnai code 61 covers how Rinnai's code system reads.
Written by [Eric Olson](/about/eric-olson), Licensed Master Plumber, Olson Superior Plumbing, Orange County, CA. Field figures come from Olson Superior's own service records. Code definitions and diagnostic sequences come from Rheem's published service documentation: the SVC 820 tankless troubleshooting manual for the legacy `11` path and the IKONIC RTGH technical training and service manual for the `A011` path. The 8 to 19 grains per gallon hardness range is a municipal water-district figure.
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