Quick answer
Noritz error code 11 means ignition failure: the heater sees a demand for hot water but cannot light, or it lights and the flame rod does not detect flame. The unit locks out on its own. Check that the gas shut-off is open and other gas appliances work, then reset once. If code 11 returns, call a licensed gas technician. If you smell gas, leave and call Enbridge Gas.
Noritz error code 11 means the water heater tried to fire and failed. Noritz's knowledge base describes it as an ignition failure: the unit registers a demand for hot water but cannot ignite, or it ignites and the flame rod never confirms a flame. Either way the control stops the gas and displays 11. Codes and reset steps differ between Noritz models, so the chart in your owner's manual and the label inside the front cover outrank any general guide.
Is code 11 dangerous, and can you keep resetting it?
The lockout is the safety system working. The heater has shut its gas valve and stays off until it is reset, so a displayed 11 with no gas smell is a no-hot-water problem, not an emergency. What you should not do is reset it over and over. Each attempt releases gas for a few seconds before the control gives up, and repeating that fixes nothing about what stopped the flame.
A gas smell changes everything. Leave the house, do not touch switches, and call Enbridge Gas at 1-866-763-5427 from outside; what to do if you smell gas has the full sequence.
The one safe check: gas supply, then a single reset
- Find the gas shut-off on the pipe below the heater. The handle should run in line with the pipe; a handle sitting across the pipe means closed.
- Try another gas appliance. If the range or the furnace will not light either, the problem is the supply and not the heater.
- On propane, read the tank gauge. Rural properties around Caledon, Kilbride, Campbellville and Carlisle sit beyond the natural gas mains, and a tank that has run low is one of the first things to rule out.
- Close every hot tap, turn the heater off and back on at its controller, then open one hot tap and listen. That is your one reset.
If 11 comes back, stop. Leave the cover on: the igniter, flame rod and gas valve behind it are licensed gas work in Ontario.
Air, gas, spark: what stops a Noritz from lighting
Noritz frames code 11 around the three things a burner needs: air, gas and spark. Its guidance is that air is rarely the one missing, which narrows a real diagnosis to spark and gas. In order of likelihood:
- Not enough gas reaching the burner. A closed or half-closed valve, air left in the line after meter or piping work, a low propane tank, or a gas line that cannot feed the heater at full fire. A tankless burner draws far more gas at once than a tank does, so a line sized for the old tank can starve it, and the shortfall shows when the furnace is firing at the same moment.
- No spark, or a weak one. The igniter electrode fouls or cracks, its lead works loose, or the gap drifts. With a tap open you would normally hear rapid ticking for a few seconds; silence can point to the spark side.
- A dirty flame rod. The burner lights, but an oxide coating on the rod blocks the tiny current the control uses to prove flame, so the control shuts the gas and records a failed ignition.
- Air, least often: a blocked intake or exhaust termination outside.
What a technician tests, and what a code 11 repair costs
Diagnosis is done with a manometer and a meter. The technician measures gas pressure at the heater's inlet while the burner tries to fire and the other gas appliances are running, because a supply that looks fine at rest can sag under load. Then the igniter is checked for spark, and the flame rod is pulled, cleaned and tested. On a heater that has gone years without service, that cleaning can be the whole repair.
- Diagnosis on site: $90–$150, which the repair invoice then absorbs.
- Water heater repairs in general: $150–$800 depending on the part.
- Gas line upsizing, when the existing line cannot feed the heater: adds $400–$1,200.
- Annual descale flush, worth pairing with the repair on hard Halton or Hamilton water: $150–$300.
Igniter and flame rod prices vary by Noritz model, so the exact figure comes as a written quote after diagnosis. Our answer on what tankless water heater repair costs breaks the ranges down.
Call once the code has returned after a single reset. ZK Mechanical is owner-operated out of Burlington, every technician holds a TSSA gas licence, and tankless water heater repair is booked at (647) 801-1252 or through the contact page. For the rest of the chart, see the Noritz tankless error code guide; if your display shows 90 instead, that is a combustion fault covered in Noritz error code 90.