Rheem Tankless Water Heater Code 11 Error
What it means
Code 11 on a Rheem (and the closely related Ruud) gas tankless water heater means 'no ignition' — the unit tried to light the burner but no flame was detected. It applies only to gas-fired models, not electric ones. The usual culprits are a gas-supply problem (valve closed, low pressure, or air in the line) or a dirty/defective igniter, flame sensor, or spark electrode. Most cases trace back to gas delivery or a dirty sensing rod rather than a major part failure. Because it's a gas appliance, only do the external checks yourself and leave internal work to a pro.
The bottom line on the Code 11 error
Code 11 means the burner tried to light and no flame was detected, and on a gas unit the most common causes are gas-supply problems - a valve left partly closed or an empty propane tank - not a failed part. If you ever smell gas, stop and call your gas utility first.
Start with the free external checks: confirm the gas valve is fully open, power-cycle the unit for 30 seconds, and clear a blocked vent. If Code 11 returns, the igniter, electrode, or flame rod likely needs cleaning or replacement - burner work a licensed plumber or Rheem-authorized technician should handle.
Code 11 snapshot
This is a gas combustion fault — if you ever smell gas, shut off the gas and leave the area, then call your gas utility first; leave the igniter, flame rod, and any internal burner work to a licensed technician.
Our own at-a-glance triage of the Code 11 error, from the verified data on this page. See error-code rankings → · How we score →
Common causes of the Code 11 error
- Manual gas valve to the heater is closed or only partly open
- Low gas pressure or air in the gas line (often after gas service, a new install, or a propane refill)
- Empty propane tank or tripped LP excess-flow valve
- Defective igniter coil — a very common cause of Code 11
- Dirty, misaligned, or sooted spark electrode / flame-sensing rod
- Blocked intake or exhaust venting limiting combustion air
Which Rheem tankless water heaters get the Code 11 error
Code 11 shows up across Rheem's gas tankless lineup and the near-identical Ruud units — including the RTGH / RTG condensing and non-condensing series, the Prestige and Performance Platinum families, and their outdoor and propane variants — on both natural-gas and LP models, because they share the same no-ignition flame-detection logic. It applies only to gas-fired tankless heaters, not electric ones.
How to fix the Rheem Tankless Water Heater Code 11 error
- 1Make sure the gas is onConfirm the manual gas valve serving the heater is fully open and that other gas appliances in the home work. For propane, check the tank isn't empty and its valve is open. A closed valve or empty LP tank is the most common reason for Code 11.
- 2Power-cycle the unitTurn the heater off for about 30 seconds (use its switch, unplug it, or flip the breaker), then power it back on and run hot water. Code 11 is a lockout, so a reset is required after the cause is fixed.
- 3Clear air from a recently serviced lineIf Code 11 appeared right after gas work, an install, or a propane refill, air may be trapped in the line. Cycling the unit a few times usually lets it draw gas through. If you ever smell gas, stop and call your gas utility or a plumber.
- 4Inspect the ventingCheck the outdoor intake and exhaust terminations for debris, nests, snow, or ice, and make sure airflow is unobstructed. Air is essential to ignition, so a blocked vent can trigger Code 11.
- 5Have a tech check the igniter, electrode, and wiringReseat the front cover and, if comfortable, look for obvious loose or corroded wiring at the ignition and flame rod. If the code persists, the igniter coil, spark electrode, or flame rod likely needs cleaning or replacement — work that involves the gas/burner assembly and should be done by a qualified technician.
🧰 When to call a professional
Call a licensed plumber or Rheem-authorized technician if Code 11 returns after confirming the gas is on and resetting the unit, if you ever smell gas (leave the area and contact your gas utility first), or if the fix requires opening the unit to reach the igniter coil, spark electrode, flame rod, gas valve, or internal wiring. Gas tankless heaters carry gas-leak and carbon-monoxide risks, so combustion and internal repairs should be left to a professional.
Rheem Code 11 vs Rinnai Code 11 vs Navien E003: how they compare
How this code stacks up against related error codes for difficulty, urgency, and cost.
| Rheem Code 11 | Rinnai Code 11 | Navien E003 | |
|---|---|---|---|
| DIY difficulty (1–5) | 5 | 5 | 5 |
| Urgency (1–5) | 4 | 4 | 4 |
| Typical cost | $$ | $$ | $$ |
How much does it cost to fix the Code 11 error?
| DIY fix (open gas valve, reset, purge air, clear vent) | Free |
| Professional repair (igniter / flame rod cleaning or replacement + labor) | $150–$400 |
| Replacement (new gas tankless unit installed) | $1,500–$4,500 |
Repair or replace?
Code 11 is very often a free fix — a gas valve left partly closed, air in a newly serviced line, or an empty LP tank — so try those before spending anything. If an igniter or flame rod is the culprit, the parts are relatively inexpensive and the repair is well worth it on a unit under roughly 12 years old, since gas tankless heaters commonly last 15–20 years. Only a much older unit already needing other repairs should tip you toward replacement under the 50% rule (replace if the repair costs more than half a new unit). Prices vary by model and region.
Common replacement parts for the Code 11 error
| Flame rod / sensing electrode | $20–$75 | OEM Rheem/Ruud part; confirms the flame | |
| Igniter / ignition electrode | $40–$100 | If the burner never sparks to light | |
| Plumber / Rheem-authorized service call | $100–$250 | Per visit; labor added to parts |
Prices are typical retail ranges and vary by model and supplier — always confirm the exact part number for your appliance before buying. We are not linking parts for this code on purpose: it is a job for a qualified technician, and the right fix here starts with a diagnosis, not a purchase.
Rheem Code 11 error — FAQ
＋ − What does Code 11 mean on a Rheem tankless water heater?
Code 11 means 'no ignition' on a gas Rheem (or Ruud) tankless unit — it tried to light the burner but no flame was detected. It's typically caused by a gas-supply issue or a dirty/defective igniter, spark electrode, or flame sensor.
＋ − How do I clear Rheem Code 11 myself?
Confirm the gas valve to the heater is fully open and other gas appliances work, then power-cycle the unit off for about 30 seconds and back on, and run hot water. If Code 11 keeps coming back, the igniter, electrode, flame rod, or venting needs a technician.
＋ − Why does Rheem Code 11 keep coming back?
A recurring Code 11 usually means an unresolved gas-delivery problem (low pressure, air in the line, empty LP tank) or a failing igniter coil or dirty flame rod. Once the root cause is corrected, the lockout clears after a reset.
Sources & manufacturer references
This guide is independently written and not affiliated with Rheem. Always unplug appliances before servicing and follow your model's manual. Error codes and steps can vary by model — when in doubt, consult a qualified technician.