What causes Noritz Tankless Water Heater 11?

The gas supply valve to the heater is closed or only partly open. Air in the gas line, common after a new installation or after the gas has been shut off. Not enough gas reaching the heater: a problem at the gas meter, regulator, gas piping or shutoff valves, or a tripped earthquake safety shutoff valve where one is installed. Build-up on the ignition rod preventing a spark, or a corroded or pitted ignition rod. A failed high-voltage cord, a failed igniter, or (least likely) a circuit board not sending voltage to the igniter. Build-up on the flame rod, a damaged or disconnected flame rod wire, or loose ground wires, so the heater lights but doesn't detect the flame. Draining the heater with the gas valve closed, which Noritz says can show 11 without anything being wrong.

How do I fix Noritz Tankless Water Heater 11?

If you smell gas, stop, leave the house and call your gas utility from outside. Don't reset or relight anything. Check that the gas valve on the line feeding the water heater is fully open. If other gas appliances aren't working either, the problem is the gas supply to the house; call your gas utility or propane supplier. Reset the heater the way Noritz's owner's guides describe: turn the heater off with the power button, open a hot water faucet, then turn the heater back on. On newer models the code also clears when you close and reopen the hot water fixture. If the blinking number doesn't come back, the problem is solved. If the heater was just installed or the gas was recently shut off, try the reset a few more times, since air in the gas line can take a couple of tries to clear. If you had just drained the heater with the gas off, code 11 is expected. Turn the gas back on and reset it. On propane, check that the tank isn't empty or nearly empty. If code 11 keeps coming back, call a licensed plumber or gas technician, or Noritz support. Removing the burner cover to clean the ignition and flame rods and checking gas pressure are jobs for a professional.

When should I call a pro for Noritz Tankless Water Heater 11?

Watching the burner through the sight glass to tell whether it is failing to ignite or igniting but failing to detect flame, which Noritz's knowledge base names as the first troubleshooting step. If there is no spark: pulling and cleaning the ignition rod (Noritz suggests the rough side of a sponge), replacing it if it is badly corroded or pitted, ideally with a new gasket on hand, then checking the high-voltage cords, the igniter and finally the circuit board. If there is spark but no flame: checking the gas supply outside the heater (meter, regulator, gas line sizing, shutoff valves, earthquake valve) and the gas supply pressure, then components inside the heater. If the burner lights but code 11 still shows: cleaning the flame rod, checking that its wire is connected and not pinched or broken, and making sure all green ground wires are secure at their grounding points. Contacting Noritz technical support with the model and serial number if the code persists after these checks.

Code: 11🚿 Noritz Tankless Water Heater

Noritz Error Code 11: Ignition Failure (Meaning, Causes, Fixes)

Q: What does Noritz Tankless Water Heater 11 mean?

Code 11 on a Noritz tankless water heater means ignition failure: the heater sees a call for hot water but can't light the burner, or lights it but doesn't detect the flame. Start by making sure the gas valve is open and resetting the heater. If it keeps coming back, the usual suspects are a dirty igniter or flame rod, or not enough gas reaching the unit, and gas checks belong to a professional. Noritz owner's guides list error code 11 as Ignition failure. Noritz's knowledge base explains that the unit recognizes a demand for hot water but can't ignite, which usually means there is no spark or not enough gas reaching the burner. In some cases the burner does light but the heater fails to detect the flame through its flame rod, and that also shows as 11. A first-time code 11 right after installation or gas work is often air in the gas line: the owner's guides say to reset the heater and try again, since there may be air in the line, and to have a professional check gas supply pressure if it still won't light. Code 11 can also appear harmlessly when you drain the heater with the gas valve closed (for example to protect it from freezing). Noritz's owner's guide says that is not a malfunction.

Reviewed 2026-10-23 · Based on 4 manufacturer & service sources

What the code means

Noritz owner's guides list error code 11 as Ignition failure. Noritz's knowledge base explains that the unit recognizes a demand for hot water but can't ignite, which usually means there is no spark or not enough gas reaching the burner. In some cases the burner does light but the heater fails to detect the flame through its flame rod, and that also shows as 11. A first-time code 11 right after installation or gas work is often air in the gas line: the owner's guides say to reset the heater and try again, since there may be air in the line, and to have a professional check gas supply pressure if it still won't light. Code 11 can also appear harmlessly when you drain the heater with the gas valve closed (for example to protect it from freezing). Noritz's owner's guide says that is not a malfunction.

Likely causes

The gas supply valve to the heater is closed or only partly open
Air in the gas line, common after a new installation or after the gas has been shut off
Not enough gas reaching the heater: a problem at the gas meter, regulator, gas piping or shutoff valves, or a tripped earthquake safety shutoff valve where one is installed
Build-up on the ignition rod preventing a spark, or a corroded or pitted ignition rod
A failed high-voltage cord, a failed igniter, or (least likely) a circuit board not sending voltage to the igniter
Build-up on the flame rod, a damaged or disconnected flame rod wire, or loose ground wires, so the heater lights but doesn't detect the flame
Draining the heater with the gas valve closed, which Noritz says can show 11 without anything being wrong

Safe DIY checks

⚠ Before you start

Unplug the appliance (or switch off its breaker) and shut off the water supply valves before removing panels or disconnecting hoses. Keep towels handy for residual water.

If you smell gas, stop, leave the house and call your gas utility from outside. Don't reset or relight anything.
Check that the gas valve on the line feeding the water heater is fully open. If other gas appliances aren't working either, the problem is the gas supply to the house; call your gas utility or propane supplier.
Reset the heater the way Noritz's owner's guides describe: turn the heater off with the power button, open a hot water faucet, then turn the heater back on. On newer models the code also clears when you close and reopen the hot water fixture. If the blinking number doesn't come back, the problem is solved.
If the heater was just installed or the gas was recently shut off, try the reset a few more times, since air in the gas line can take a couple of tries to clear.
If you had just drained the heater with the gas off, code 11 is expected. Turn the gas back on and reset it.
On propane, check that the tank isn't empty or nearly empty.
If code 11 keeps coming back, call a licensed plumber or gas technician, or Noritz support. Removing the burner cover to clean the ignition and flame rods and checking gas pressure are jobs for a professional.

🛠 When to call a pro

Watching the burner through the sight glass to tell whether it is failing to ignite or igniting but failing to detect flame, which Noritz's knowledge base names as the first troubleshooting step.
If there is no spark: pulling and cleaning the ignition rod (Noritz suggests the rough side of a sponge), replacing it if it is badly corroded or pitted, ideally with a new gasket on hand, then checking the high-voltage cords, the igniter and finally the circuit board.
If there is spark but no flame: checking the gas supply outside the heater (meter, regulator, gas line sizing, shutoff valves, earthquake valve) and the gas supply pressure, then components inside the heater.
If the burner lights but code 11 still shows: cleaning the flame rod, checking that its wire is connected and not pinched or broken, and making sure all green ground wires are secure at their grounding points.
Contacting Noritz technical support with the model and serial number if the code persists after these checks.

Sources

Last reviewed 2026-10-23. Always confirm against the manual for your exact model number.

Noritz Error Code 11: Ignition Failure (Meaning, Causes, Fixes)

What the code means

Likely causes

Safe DIY checks

🛠 When to call a pro

Related codes

Sources