Noritz Code 16: Abnormal Gas Combustion or Pressure Fault

Quick Answer

Noritz Code 16 indicates a gas pressure fault. The unit detected that incoming gas pressure is either too low (below 3.5 inches water column for natural gas) or too high (above 10.5 inches water column), causing abnormal combustion. Low pressure is more common and is typically caused by an undersized gas meter, a failing regulator, or peak demand on the utility line. High pressure is less common but can result from a failed regulator that has stuck open. A licensed plumber or gas technician is required to test and adjust gas pressure.

NoritzWaterheaterSeverity: highDifficulty: intermediate70% DIY Success

Time to Fix

60–180 min

Difficulty

intermediate

Parts Cost

$40 – $280

Tools Needed

Manometer (required for gas pressure test), Multimeter

Wrong code?

Not seeing 16 on your display?

Select what your appliance is actually doing and we'll take you to the right guide.

error code on display

HUB

no ignition

flame lost during use

error code on display

RESET

What Does the 16 Code Mean?

Gas supply pressure outside the 3.5 to 10.5 in WC acceptable range for natural gas. Professional pressure testing required.

Most Likely Causes

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

Gas supply pressure too low due to undersized meter or regulator40%

Gas supply pressure too high from failed regulator24%

Gas valve fault causing incorrect pressure reading22%

Gas meter undersized for total building demand14%

Symptoms You May Notice

Code 16 on controller display
Unit shuts down during or immediately after ignition
Code 16 occurring during peak gas demand hours
Other gas appliances may run weakly or with reduced output

Can you reset a Noritz waterheater to clear the 16 code?

Press the power button off, wait 30 seconds, then press on. Code 16 will clear temporarily but will return if pressure remains outside the acceptable range. Do not continue resetting without addressing the pressure issue.

Tools Required for Diagnosis

Manometer (required for gas pressure test)Multimeter

Diagnostic Checklist

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

Confirm other gas appliances (furnace

Confirm other gas appliances (furnace, range, dryer) are working and operating with normal flame height and output. This gives a quick read on whether the issue is at the street level or specific to the water heater.

Locate the gas pressure test port on the unit's gas valve (small

If pressure is low

Check the gas meter capacity rating (listed on the meter body in

If pressure tests are all within spec

Replacement Parts

If your diagnostic testing proves the component has failed, you will need a replacement. We recommend OEM parts over aftermarket for water-handling components.

Part Name	OEM Number	Estimated Price
Gas Valve Assembly100161840 · $150–$280	100161840	$150 – $280
Building Gas RegulatorN/A - plumber supplied · $40–$120	N/A - plumber supplied	$40 – $120

Verify part fitment for your Noritz model

Repair vs. Replace Calculator

Appliance Age (Years)7 Yrs

Labor Approach

Our Verdict

REPAIR

Estimated Cost: $160 (Parts) vs $1150 (New Machine)

Frequently Asked Questions

What gas pressure does a Noritz tankless water heater require?

Noritz water heaters require natural gas supply pressure between 3.5 and 10.5 inches water column (0.87 to 2.61 kPa). The ideal working pressure is around 7 inches WC. For propane (LP) models, the range is different - check your specific model's installation guide.

Can low gas pressure damage my Noritz water heater?

Operating at very low gas pressure causes incomplete combustion, which produces elevated carbon monoxide and deposits soot on the heat exchanger and burner. Over time this damages the combustion components. Code 16 is the safety system preventing this from happening. Do not bypass or repeatedly reset Code 16.

Why does Code 16 only happen in winter?

In winter, gas demand across the utility grid increases significantly. Distribution pressure at the meter can sag during peak morning and evening hours. If your regulator or meter is already at the margin of adequacy, the drop can push pressure below the 3.5 in WC minimum and trigger Code 16. The same home may never see Code 16 in summer.

Does Code 16 mean I have a gas leak?

Not directly. Code 16 is a pressure measurement fault, not a leak detection alert. However, abnormally high pressure (above 10.5 in WC) can stress fittings and connections over time. If you notice a gas smell alongside Code 16, do not reset - shut off the gas supply valve and call the gas utility.

How do I know if my gas meter is too small for a tankless water heater?

Look at the BTU/hr or CFH rating stamped on the meter body. Add up the BTU input ratings for all gas appliances: furnace, range, dryer, and the water heater. If the total exceeds the meter rating, the meter is undersized. A Noritz NRCP199-DV, for example, has a 199,000 BTU/hr input rating, which is a significant addition to a home's gas load.

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: RESETHow to Reset a Noritz Tankless Water Heater and Clear Error Codes

Models Known to Experience 16 Errors

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

NRCP199-DV, NRCP111-DV, NR98-DV, NR66-DV, NR711

Last verified for technical accuracy on March 14, 2026