Noritz tankless water heaters diagnose faults through an on-screen error code, most often ignition failure, scale buildup or a high limit trip. National repair costs run $100 to $650, averaging $375, per Fixr's tankless data. Noritz's standard warranty covers the heat exchanger 12 years, parts 5 years and labor 1 year, longer on select EZ Series models.
Hot Water Brief is an independent cost-research site. We are not a contractor and do not perform the work ourselves.
Each code reports which safety check failed, not which part to swap. Noritz spreads its codes across several posts and a knowledge base rather than one master chart; the table below combines what those pages say about the codes homeowners see most often.
| Code | What it reports | Recommended step |
|---|---|---|
| 11 | Ignition failure: no gas, spark or air present | Confirm the gas valve is open; contractor checks pressure and spark |
| 12 | Flame lights but will not hold | Contractor checks gas pressure with a manometer |
| 16 | Scale cutting heat transfer, outlet temperature spikes | Annual descaling or a softener; contractor if it persists |
| 20 | High limit switch tripped at 176 to 205 degrees F, usually from scale | Descale flush and combustion cleaning; repeated resets risk code 14 |
| 29 | Condensate drain blocked or misrouted | Clear the drain line and container |
| 73 | Circuit board settings changed during operation | Unplug 30 seconds and restart; contractor if it returns |
| 90 | Combustion abnormality after three failed attempts on temperature | Contractor checks gas pressure, venting and dip switches |
| F76 | Communication breakdown between two Quick-Connected units | Confirm only one remote connected; contractor if it continues |
Source: Common Noritz Tankless Error Codes, 21 May 2019; Five Common Tankless Error Codes, 6 June 2022; Error Code 20, updated 15 July 2022; Seven Most Common Noritz Tankless Error Codes, 16 November 2015, all Noritz.
A flow fault can show no code at all: demand below about 0.5 gallons per minute sits under the unit's minimum activation flow, so it simply never fires, per Noritz. The problems and error code guide covers code 16 alongside Navien's equivalent codes.
Three failure points account for most Noritz tankless service calls: scale on the heat exchanger, ignition trouble from gas supply or airflow, and a blocked condensate drain. Noritz's knowledge base ties code 20, a high limit trip, to the same scale behind code 16, so the two often arrive together.
Water hardness drives the scale-related pair. Noritz's warranty document excludes damage from water harder than 12 grains per gallon, 200 mg/L, or high pH, the company's own line for when treatment stops being optional. Noritz states the average unit lasts 10 to 25 years depending on maintenance, and recommends annual service to reach the long end.
Repeated high limit trips are worth taking seriously rather than clearing through. Noritz's knowledge base warns that resetting code 20 without fixing the cause risks escalating to code 14, a more involved repair. Ignition failures, codes 11 and 12, trace to gas supply, a low propane tank, airflow or debris on the ignition plug, not the burner itself. Condensate faults, code 29, are often a drain piping issue rather than a failed part.
Noritz's standard residential warranty covers the heat exchanger for 12 years, other parts for 5 years and labor for 1 year, rising to 25 years on the heat exchanger for EZ Series models in a single-family home. Coverage starts on the installation date or 30 days after purchase, whichever comes first, per Noritz's current warranty page.
| Coverage | Standard residential | EZ Series, single family |
|---|---|---|
| Heat exchanger | 12 years | 25 years |
| Other parts | 5 years | 5 years |
| Labor | 1 year | 1 year |
Source: Noritz, Product Registration and Warranty Terms, accessed August 2026.
The same page excludes damage from non-potable water, poorly treated well water, or water harder than 12 grains per gallon (200 mg/L) or high pH, plus damage from improper installation, improper maintenance, freezing, unauthorized modification and misuse. That hardness figure is worth checking against a water test before assuming a scale failure is covered, since it targets exactly the failure behind codes 16 and 20.
On paper, Noritz's standard 12-year heat exchanger term is shorter than Navien's 15 years and Rinnai's 15 years, though Noritz's EZ Series beats both at 25 years. All three cap labor at 1 year unless a condition is met: Rinnai extends labor to 5 years for units registered within 90 days of install.
| Brand, line | Heat exchanger | Parts | Labor |
|---|---|---|---|
| Noritz, standard | 12 years | 5 years | 1 year |
| Noritz, EZ Series | 25 years | 5 years | 1 year |
| Navien NPE-A, controlled recirc | 15 years | 5 years | 1 year |
| Navien NPE-A, uncontrolled recirc | 5 years | 3 years | 1 year |
| Rinnai SE+, registered within 90 days | 15 years | 5 years | 5 years |
| Rinnai SE+, not registered | 15 years | 5 years | 1 year |
Source: Noritz warranty page above; Navien, NPE Warranty Information, accessed August 2026; Rinnai, SE+ Series Limited Warranty, dated October 2024.
Warranty length is a coverage comparison, not a durability rating. None of the three publishes failure rate data, so heat exchanger years are the only serviceability figure that is documented and comparable across all three. Read it as coverage on paper, not a claim about which unit breaks down less.
Noritz does not publish repair prices, so the best available figures are market wide rather than brand specific. Fixr's tankless data puts the national average at $375, typically $100 to $650, with ignition failure at $100 to $300 and a scaling repair at $150 to $450.
| Repair | Typical range |
|---|---|
| Ignition failure | $100 to $300 |
| Scaling or clog issue | $150 to $450 |
| Unit shuts off | $50 to $500 |
| Low pressure or flow | $75 to $500 |
Source: Fixr, Tankless Water Heater Repair Cost, updated 31 January 2025.
Whether a part is billed at all depends on the warranty tables above. A heat exchanger inside its 12 or 25 year window should mean paying only for labor, one year of which Noritz covers from the effective date. Past that window, or on a hardness-excluded scale failure, the full range applies. See the problems and repair cost guide for the wider picture, and the cost guide for replacement figures.
Noritz's own servicer search, reachable from its knowledge base, locates local technicians by zip code, and its product specialist line handles general and warranty questions. Neither replaces confirming the company's license before it touches gas piping or the electrical connection, the buyer's step regardless of brand.
Source: Find a Local Servicer, updated 2 May 2024; Noritz, Contact Us.
Hot Water Brief does not perform repairs, sets no prices, and makes no claim about how quickly any company responds. For symptoms that are not brand specific, no hot water, a leak, a pilot that will not stay lit, the general problems and repair cost guide covers cause and typical range across any manufacturer.
Every figure on this page traces to a Noritz document or a published cost guide, listed below with its date.
Prices and warranty terms change; check these dates against today.
Scale buildup on the heat exchanger, cutting heat transfer until outlet water temperature spikes. Noritz says annual descaling or a water softener prevents it, and ties the same scale to code 20, a high limit trip. See [the problems and error code guide](/problems/) for how this compares across brands.
Ignition failure: gas, spark or air needed to light the unit is not present. Noritz says to confirm the gas valve is open, then have a licensed contractor check gas pressure and test for spark, since the cause can be a low propane tank, a supply disruption, or debris on the ignition plug.
Standard single-family installs carry 12 years on the heat exchanger, 5 years on parts and 1 year on labor, per Noritz's current warranty page. Select EZ Series models extend heat exchanger coverage to 25 years, with parts and labor unchanged.
No. Noritz's warranty excludes damage from water harder than 12 grains per gallon (200 mg/L) or high pH, along with non-potable or poorly treated well water. Since scale sits behind two of Noritz's most common codes, 16 and 20, checking hardness against that number matters first.
Noritz does not publish repair prices. Fixr's tankless data, updated 31 January 2025, puts the national average at $375, typically $100 to $650, with ignition failure at $100 to $300 and a scaling repair at $150 to $450. Warranty status changes what, if anything, gets billed for parts.
Noritz's servicer search, linked from its knowledge base, locates local technicians by zip code, and its specialist line handles general and warranty questions. Confirming the company's license before gas or electrical work begins is the buyer's step regardless of what tool located them.
Independent Research
Published ranges for tank and tankless replacement, the failures that justify a repair, and the ones that do not. Sourced, dated, and free to read.
