Rheem Tankless Water Heater Igniter/Electrode Replacement — What This Part Does
The igniter (ignition electrode) on a Rheem tankless water heater creates the spark that lights the gas burner during startup. The flame rod (flame-sense electrode) then proves ignition by detecting the flame and signaling the control board to keep the burner running. Both parts work together in the ignition sequence, and either one failing will trigger an ignition failure fault.
These components fail from heat cycling, contamination, cracks in the ceramic insulator, corrosion, or normal wear over time. When the igniter cannot produce a strong spark or the flame rod cannot sense the flame, the control board logs the failed attempt as Code 11 and locks out the unit. Gas supply issues, blocked venting, loose wiring, or burner debris can also cause ignition failure, so checking the full ignition path is necessary before assuming the electrode itself is bad.
Signs It Needs Replacing
- Code 11 or ignition failure error on the display The control tried to light the burner but did not prove ignition within the allowed time.
- No hot water and the unit does not fire The heater powers on but the burner never lights when you open a hot tap.
- Clicking or sparking sound with no flame You hear the igniter firing repeatedly but the burner does not catch and stay lit.
- Short burner run followed by immediate shutdown The burner lights briefly then cuts off because the flame rod cannot confirm stable combustion.
- Visible cracks or heavy contamination on the igniter or flame rod Inspect through the burner chamber and look for broken ceramic, corrosion, or buildup on the electrode tips.
- Repeated lockouts requiring manual reset The unit cycles through ignition attempts, fails, and requires you to reset power before it will try again.
How to Replace It
- Shut off electrical power at the circuit breaker, close the gas supply valve to the heater, and close the water inlet valve.
- Remove the front cover or service panel to access the burner chamber (consult your model’s manual for screw locations and cover removal).
- Take a photo of the wiring connections on the igniter coil and flame rod before disconnecting anything.
- Disconnect the wire harness or spade connectors from the igniter and flame rod, then remove the mounting screws or brackets holding each component in place.
- Pull the old igniter and flame rod out of the burner chamber and inspect the burner area for debris, scale, or soot that could interfere with ignition.
- Install the new igniter and flame rod in the same positions, securing them with the original mounting hardware and verifying the electrode tips are properly positioned in the flame path.
- Reconnect the wire harness to each component, matching your reference photo and checking that all connectors are fully seated.
- Reinstall the front cover, open the gas valve, open the water inlet valve, and restore electrical power at the breaker.
- Open a hot water tap to initiate a call for heat, observe the ignition sequence, and confirm the burner lights and stays on without error codes.
The Part You Need
| Part | Notes |
|---|---|
| Rheem tankless water heater igniter coil / ignition electrode | Amazon | Part number varies by model (e.g., RTG20164U or RTG20074DL). Check the model and serial plate inside the front cover or on the right side of the unit, then cross-reference with Rheem’s parts catalog or an authorized dealer. |
| Rheem tankless water heater flame rod / flame-sense electrode | Amazon | Part number varies by model (e.g., RTG20164H). Often sold separately from the igniter. Verify your exact model number before ordering. |
Related Error Codes
If this part is failing you may also see one of these codes:
When to Call a Pro
Call a licensed plumber or gas technician if you are not comfortable working with gas appliances, if the error persists after replacing the igniter and flame rod, or if you find gas leaks, blocked venting, or signs of burner damage. Gas valve replacement, combustion air adjustment, and gas-pressure testing require specialized tools and certification. If wiring or the main control board is damaged, professional diagnosis will save time and prevent further component failure. For gas line, burner, or igniter work, or if you ever smell gas, stop and call a licensed technician.