11
Noritz Tankless Water Heater
Severity: CriticalWhat it means
Noritz code 11 is ignition failure — the unit opened the gas valve, sparked, and never proved a flame, so after a few tries it locks out and you get cold water.
Start with the obvious: is the gas shutoff to the unit fully open, is there gas at all, is the propane tank low?
After that the suspects are air in the gas line, low supply pressure, a dirty igniter, or the flame-sensing rod.
The good news is most code 11s are gas-supply problems, not failed parts.
Affected Models
- Noritz NRC66, NRC83, NRC98, NRC111
- Noritz NRCP series (with built-in pump)
- Noritz EZ98, EZ111
- Noritz NR50, NR66, NR83, NR98 (non-condensing)
- Noritz GQ-C series
Common Causes
- Gas shutoff valve to the unit only partly open
- Air in the gas line — new install, gas turned off at the meter, or a propane tank just swapped
- Propane tank low, or its valve barely cracked open
- Low gas supply pressure — undersized line, or a furnace/range starving it when they run
- Igniter dirty, cracked, or out of position
- Flame-sensing (ionization) rod coated, loose, or cracked
- Gas solenoid valve coil failed
How to Fix It
-
Confirm the gas is on.
Trace the gas pipe to the unit — the shutoff handle should be in line with the pipe, not half-turned.
Check the main gas is on and that another gas appliance (a stove burner) lights normally.
If nothing gas-fired works, that's a supply problem, not the water heater. -
Bleed air from the line.
New unit, gas recently shut off at the meter, or a propane tank just changed? There's air in the pipe.
Reset and let the unit attempt ignition several times — each try purges a little air.
It can take a few cycles before it catches. -
Check the propane level if you're on LP.
A low tank can supply enough gas to spark but not enough to light reliably — and a brand-new tank may have an overfill-protection device limiting flow.
Open the tank valve slowly and fully.
Anything under about 20% on the gauge, refill before chasing parts. -
Reset and listen.
Power off, ten seconds, power on, run a hot tap.
Listen for the igniter clicking and the burner lighting.
Sparks but no flame means gas is reaching the valve but not getting through, or the igniter isn't doing its job. -
Have the gas pressure measured.
A plumber or gas tech puts a manometer on the inlet and checks pressure while the unit fires at full rate — and while other gas appliances run.
An undersized or shared gas line is a very common code 11 cause, and resetting won't fix it; the line has to be upsized. -
Inspect or replace the igniter and flame rod, then call service.
Breaker off.
A cracked ceramic igniter, a sooted flame-rod tip, or a loose wire all cause repeated ignition failure — clean or replace them.
If gas, pressure, igniter and flame rod all check out and it still won't light, the gas solenoid valve is the suspect, and that's a Noritz service repair.