Noritz Tankless Water Heater Troubleshooting & Common Fixes

Quick Answer

Start with the error code shown on the display and use the specific code guide. If no code is shown, check that flow rate exceeds 0.5 GPM, the gas valve is open, and the vent terminations are clear. A soft reset (power off 30 sec, power on) clears temporary faults.

Most of the time when I get called out for a Noritz that's acting up, it's one of three things: scale buildup nobody flushed in years, a vent that's partially blocked, or a flow rate that's just barely under the activation threshold. Ignore any of these long enough and you're looking at a heat exchanger replacement, which honestly costs more than some new units. Don't let it get there.

NoritzWaterheaterSeverity: moderate70% DIY Success

Time to Fix

15–60 min

Difficulty

beginner

Parts Cost

$0 (no parts needed)

Tools Needed

Phillips #2 screwdriver, Flathead screwdriver

Noritz Tankless Water Heater Troubleshooting & Common Fixes

OK so here's the deal with Noritz tankless units. They're solid machines, but they're particular about flow rate, gas pressure, and venting. If your display is showing a code, go to that specific code page because each one has a completely different fix. No code showing? That's actually trickier sometimes. Use the symptom sections below to work through it.

Most Likely Causes

Based on aggregated repair data, here is the probability breakdown for this error code:

Error code triggered - consult specific guide40%

Flow rate too low to activate unit25%

Scale buildup in heat exchanger20%

Vent or exhaust issue15%

Symptoms You May Notice

You turn on the hot tap and get maybe 30 seconds of warm water then it goes stone cold
The unit makes a clicking sound like it's trying to ignite but never actually fires
Hot then cold then hot again every minute or two during a shower, like someone keeps flipping a switch
Water dripping from the bottom of the unit onto the floor below
Unit fires up and heats water fine, then cuts out completely after 5 to 10 minutes of use

Can you reset a Noritz waterheater to clear the TROUBLESHOOTING code?

Soft reset: press the power button to turn the unit off, wait 30 full seconds, then press it again. Hard reset: disconnect power at the breaker for 60 seconds then restore. Run hot water for 2 minutes after either reset to confirm the unit fires. Code 14 faults won't clear with any reset because the thermal fuse is physically blown and needs replacement before the unit will run again.

Tools Required for Diagnosis

Phillips #2 screwdriverFlathead screwdriverAdjustable wrenchMultimeter1-gallon bucket and timer (for flow rate test)Flashlight or headlampFine steel wool (for flame rod cleaning)Descaling flush kit with pumpFood-grade white vinegar or commercial descaling solution

Diagnostic Checklist

Follow these steps in order. We start with the easiest external fixes before opening up the machine.

Did the fix not work?

If the problem comes back after following these steps, a component has permanently failed and needs replacement. Check the specific error code your waterheater is showing:

HUB Error →11 Error →12 Error →NO-HOT-WATER Error →

Frequently Asked Questions

Why does my Noritz water heater click but not ignite?

That clicking is the spark igniter doing its job. The problem is nothing's catching. First thing to check is whether gas is actually on at the unit. Go test another gas appliance in the house. If gas is good, the flame rod is the next suspect. It's a small metal probe sitting in the burner chamber and it gets coated with carbon and oxide over time, especially if the unit sees a lot of short cycles. Cleaning it with fine steel wool usually fixes it. I replaced three flame rods last month alone on units that were just dirty, not actually broken. Check the Code 11 article for the full repair sequence.

Why does hot water go cold then hot again in my Noritz?

That's the cold water sandwich effect, and honestly it's not a malfunction. It's just how tankless heaters work. Here's what's happening. You ran hot water earlier so the pipes between the heater and your tap are loaded with hot water. When you turn the tap on again, that leftover hot water comes out first. Then you get a slug of cold water that entered the pipes after your last draw, before the unit heated it. Then finally you get fresh hot water. The longer the pipe run between the unit and the tap, the worse it feels. A recirculation pump basically eliminates this. Pre-flushing for 10 seconds also helps.

How often should a Noritz tankless water heater be serviced?

Noritz recommends annual inspection and descaling in hard water areas, which they define as above 11 GPG hardness. In soft water areas a 2-year interval is pretty standard. But I see more units come through for repair that were never descaled than anything else. Scale buildup is the number one killer of heat exchangers. If you're in the midwest or southwest where the water is hard, do it every year without fail. A descaling kit runs about 30 bucks and takes two hours. A heat exchanger replacement is 600 to 900 dollars in parts alone. Skipping descaling is the leading cause of Code 29 and Code 14 faults.

My Noritz runs fine for a few minutes then shuts off. What causes that?

Mid-cycle shutoff is usually one of two things. Either the heat exchanger is scaled up and overheating because it can't transfer heat efficiently anymore, which shows up as Code 29, or you've got a flame rod that works fine when cold but fails once it gets hot, which triggers Code 12. The flame rod issue is tricky because the unit seems fine for a few minutes then just quits. Best move is to pull up the stored error history in service mode because it'll show you exactly which code it faulted on. Check your service manual for the button sequence specific to your model controller.

Can I troubleshoot a Noritz water heater myself or do I need a plumber?

A lot of things you can handle yourself. Resetting the unit, cleaning the intake filter screen behind the cold water inlet, checking that the gas valve is open, and clearing leaves or ice off the vent termination are all beginner-level stuff that takes maybe 20 minutes. Flame rod cleaning and descaling are intermediate, you need basic tools and you've got to be comfortable opening the unit up. But gas valve replacement, thermal fuse replacement after a Code 14, and fan motor issues are a different story. Get a licensed plumber or a Noritz-certified tech for those. Messing with gas valve internals without training is genuinely dangerous.

Related Noritz Waterheater Error Codes

Code: HUBNoritz Tankless Water Heater Error Codes: Complete NR and NRCP Series Guide Code: 11Noritz Code 11: No Ignition Fix for NR and NRCP Series Code: 12Noritz Code 12: Flame Failure During Operation Code: NO-HOT-WATERNoritz Tankless Water Heater No Hot Water: 7 Causes and How to Fix Them Code: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience TROUBLESHOOTING Errors

This repair applies to most Noritz waterheaters with this error code. Common model numbers include:

NRCP199-DV, NRCP111-DV, NRC98-DV, NR98-DV, NRC711-DV, NR711, NR66-DV, NRCP66-DV

Written by

Raj Patel

HVAC & Water Systems Specialist · 15 years experience

Last verified for technical accuracy on March 17, 2026