Navien Error Code 016: What It Means and How to Fix It

Navien error code 016 typically indicates a low water pressure or flow rate issue, which can often be resolved by clearing debris from the inlet filter or checking your home water supply valves.

Table of Contents

What does error code 016 mean on a Navien water heater?
Why is my Navien unit showing error code 016?
How do I perform quick fixes for Navien error 016?
What are the next steps if the error persists?
Which Navien fix matches your symptom?
When should I stop troubleshooting and call a technician?
What information should I have ready before calling support?
How can I prevent error code 016 from coming back?

What does error code 016 mean on a Navien water heater?

Navien error code 016 indicates a low water pressure or insufficient water flow detected within the unit.

When your Navien tankless water heater or boiler registers this error, it means the internal flow sensor is not detecting enough water movement to safely ignite the burner. This protection feature prevents the unit from dry-firing and damaging internal components, ensuring safe operation during household use.

The internal flow sensor detects insufficient water movement through the heat exchanger.
Low overall water pressure in your municipal supply or household plumbing system can trigger this.
Clogged or blocked cold water inlet filters restrict the necessary volume of incoming water.
Scale buildup or mineral deposits inside the water heater pipes can impede water flow over time.
Faulty or stuck flow control valves fail to open fully during hot water demand.

Why is my Navien unit showing error code 016?

Error code 016 is usually caused by restricted water flow from clogged inlet filters or closed supply valves.

Over time, sediment, debris, and mineral scale accumulate at various points in the plumbing system. When these blockages restrict water from entering or moving through the water heater at the required rate, the unit halts operation and displays this specific fault code.

Debris or sediment blocks the fine mesh screen inside the cold water inlet filter.
The main water supply valve leading into the tankless water heater is partially closed.
Hard water mineral scale builds up inside the internal pipes and flow components.
Multiple plumbing fixtures running simultaneously exceed the flow capacity of the unit.
A malfunctioning pressure regulator in your home plumbing reduces incoming water force.

How do I perform quick fixes for Navien error 016?

Perform quick checks on your water supply valves and clean the cold water inlet filter.

Before attempting any maintenance or troubleshooting steps, always turn off the power supply to the water heater at the circuit breaker. Ensuring the unit is powered down prevents electrical hazards while you inspect and service the external plumbing connections.

Turn off the power switch on the water heater and trip the dedicated circuit breaker.
Locate the cold water shut-off valve on the right side of the unit and ensure it is fully open.
Place a small towel underneath the cold water inlet filter plug to catch any trapped water.
Unscrew the cold water inlet filter cap and carefully pull out the mesh filter screen.
Rinse the filter screen under clean running water to remove any trapped debris or sediment.
Reinsert the clean filter securely, tighten the cap, open the water valve, and restore power.

What are the next steps if the error persists?

Inspect for mineral scale buildup and flush the heat exchanger if simple cleaning fails.

If clearing the inlet filter does not resolve the error code, the restriction may be located deeper within the system. Mineral scale buildup can severely choke flow rates in hard water areas, requiring a thorough chemical flush of the internal heat exchanger coils.

Turn off the electrical power breaker to the water heater before handling internal components.
Close the hot and cold water isolation valves connected to the service ports on the unit.
Connect a submersible descaling pump and hoses to the cold water service flush port.
Circulate food-grade white vinegar through the system for forty-five to sixty minutes.
Flush the system thoroughly with clean water, disconnect the hoses, and reopen the service valves.

Which Navien fix matches your symptom?

Match your specific operational symptom to the corresponding likely cause and recommended fix.

Symptom	Likely cause / fix
Error appears when multiple taps run	Exceeds flow capacity / reduce hot water demand
Error appears with low pressure everywhere	Main home water pressure is low / check supply
Error code stays on after filter cleaning	Scale inside heat exchanger / flush system
Error occurs only at one specific faucet	Clogged aerator at fixture / clean aerator screen

When should I stop troubleshooting and call a technician?

Stop troubleshooting and call a licensed professional if gas components or internal electrical parts are involved.

Safety is paramount when dealing with tankless water heaters and boilers. If basic filter cleaning and descaling do not clear error 016, or if you suspect a failing internal flow sensor or electronic control board, professional service is required to prevent further damage.

Stop immediately if you smell gas or suspect a gas leak around the appliance.
Call a professional if internal electrical wiring or high-voltage control boards need testing.
Contact an expert if the flow sensor or internal water valve requires replacement.
Engage a licensed plumber if your home has persistent low water pressure issues.
Stop if you are uncomfortable performing any maintenance steps safely.

What information should I have ready before calling support?

Gather your exact unit model number, serial number, warranty status, and troubleshooting steps tried.

Having accurate details ready when you contact manufacturer support or a local technician ensures a faster diagnosis and more efficient service appointment. Locate the metal rating plate on the side cabinet of your Navien unit to find the required identification data.

Locate and write down the complete model and serial number from the unit rating plate.
Note the date of purchase and check the remaining manufacturer warranty status.
List all specific troubleshooting steps you have already performed, such as cleaning filters.
Record whether the error code appears continuously or only when specific faucets are opened.
Keep your home address and contact information ready for the service dispatcher.

How can I prevent error code 016 from coming back?

Prevent future occurrences by performing annual filter inspections and routine water heater flushes.

Proactive maintenance is the best defense against recurring error codes in tankless water heaters and boilers. Establishing a regular schedule for cleaning inlet screens and managing mineral buildup keeps water flowing freely and extends the lifespan of your appliance.

Inspect and clean the cold water inlet filter screen every six months.
Flush the heat exchanger annually with white vinegar to prevent hard water scale accumulation.
Install a whole-house water softener if your municipal or well supply has high mineral content.
Check home water shut-off valves periodically to ensure they remain fully open.
Monitor household water pressure gauges to catch supply fluctuations early.

Frequently Asked Questions

What should I do if error code 016 comes back immediately after cleaning the filter?

If the error returns right away, scale buildup inside the heat exchanger is likely restricting flow. You should perform a vinegar flush of the system or check if the internal flow sensor is obstructed by debris that bypassed the filter screen.

Can a failing water pressure regulator in my home cause this Navien error code?

Yes, a failing pressure regulator can drop your overall incoming water pressure below the threshold required by the Navien unit. Testing your home water pressure with a gauge attached to an outdoor spigot can help confirm this issue.

Is it safe to clean the Navien inlet filter myself without professional help?

Cleaning the cold water inlet filter is a routine homeowner maintenance task designed for easy access. Always remember to turn off the electrical power breaker and close the water supply valves before opening any filter caps.

Why does error 016 happen only when I run multiple showers at the same time?

Running multiple high-flow fixtures simultaneously can exceed the maximum flow rate capacity of your specific water heater model. Reducing simultaneous hot water usage will usually prevent the unit from triggering this low-flow protection fault.

Will resetting the water heater clear error code 016 permanently?

Resetting the unit will only clear the code temporarily if the underlying physical restriction remains unresolved. You must clean the inlet filter or clear scale blockages to stop the error from returning during normal operation.

Bottom Line

Start by turning off the power breaker and inspecting the cold water inlet filter for trapped debris. This quick step resolves most low flow issues safely.

Sources

Navien owner’s manual
Navien installation manual
Manufacturer support page