Rinnai Tankless Error Codes List: 10, 11, 12, 14, LC

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Quick answer from a licensed plumber: the number flashing on a Rinnai tankless controller is a diagnostic code, and Rinnai says the heater shuts down when an error occurs. The codes an owner is most likely to be able to act on are 11 (No Ignition), 12 (No Flame), 10 (air supply or exhaust blockage, or a full condensate trap) and 14 (heat exchanger overheat). SS and LC mean the heat exchanger needs flushing. Start with the checks you can make outside the cabinet: gas turned on, propane in the tank, the vent terminal and condensate line clear, the filters clean. Apart from the air filter, anything behind the front panel — the flame rod, igniter, gas valve or circuit board — is work Rinnai assigns to a trained and qualified professional.

Safety first: if you smell gas, do not try to light any appliance, do not touch any electrical switch or use any phone in the building, and call your gas supplier from a neighbor’s phone (the fire department if you cannot reach them). That is Rinnai’s own instruction. Rinnai also says not to use the water heater if any part has been under water, and not to run it while the unit or its piping is frozen.

Rinnai Codes at a Glance

The meanings below are Rinnai’s own wording from the Diagnostic Codes table in its manual for the SENSEI RU199, RU180, RU160 and RU130 (indoor “i” and outdoor “e”) models. Rinnai’s technician guide covers codes for its SENSEI, Value, Luxury and older KB-series heaters and notes which series each code applies to, so the table in your own manual is the final word.

Code	What Rinnai says it means	Your first move
03	Power interruption during bath fill (water will not flow when power returns)	Turn off all hot water taps and press ON/OFF twice.
05	By-pass flow control	Technician: resistance test or replace the by-pass flow control.
10	Air supply or exhaust blockage / condensate trap is full	Check the condensate line, the vent terminal and (indoor units) the air filter. See below.
11	No ignition (heater not turning on)	Gas on at the heater and meter or cylinder; propane in the tank. Then a professional.
12	No flame	Same gas checks as code 11. Then a professional.
14	Heat exchanger overheat	Rinnai lists scale build-up in the heat exchanger (flush it); the overheat switch test is technician work.
15	Venturi control	Technician. Rinnai says to clear it by resetting the main power supply.
16	High outgoing temperature (safety shutdown because water heater is too hot)	Stop using hot water and call a professional.
17	Venturi blockage	Technician: code 10 checks first, then the venturi.
19	Electrical grounding	Technician: check components for an electrical short.
21	Data transfer error	Rinnai’s check: if the circuit board was replaced, the data transfer must be completed. Technician.
25	Condensate pump (accessory)	Make sure the condensate pump is plugged in and running and its reservoir is empty.
32, 33, 38, 41, 51	Outgoing, heat exchanger, exhaust, freeze-protection and inlet thermistors (sensors)	Technician: wiring check, resistance test, clean or replace the sensor.
52	Gas valve	Technician.
54	High exhaust gas temperature	Technician: heat exchanger fins, inlet water temperature.
61	Combustion fan	Technician.
63	Recirculation low flow	Clean the inlet water filter and bypass filter; the rest is technician work.
65	Water flow control (failed to close during bath fill)	Turn off the water now, stop using bath fill, call a professional.
70, 71, 72	PC board / solenoid valve circuit / flame rod	Technician.
FF	Maintenance indicator — a record that service was done	Not a fault.
SS	Service Soon (flush heat exchanger)	Flush the heat exchanger, then reset (On/Off 5 times in 5 seconds).
LC	Lime (scale) detected in the heat exchanger, on models with Lime Check	Flush the heat exchanger. On some models LC locks the unit out.
No code	Nothing happens when water flow is activated	Open the tap wider (minimum flow), clean the inlet water filter. New install: hot and cold lines may be reversed.

Clear the Code, Then Read the History

Rinnai’s accessory instructions say that when an error occurs the water heater shuts down, and that most errors reset when the water flow stops — taps turned off, a circulating pump stopping — or when the power is switched off and on. Note that the controller’s On/Off button does not cut the power; to switch the power off you unplug the heater or turn off its circuit breaker.

A code that returns the moment you open a tap is the heater telling you the cause is still there. Rinnai’s technician guide is blunt about code 03: if it comes back after three resets, the circuit board gets replaced. Keep resetting any code and you have only delayed the diagnosis. If the heater is due for replacement, our Navien vs Rinnai comparison sets the two maker manuals side by side.

To see what the heater has been logging, the RU-series manual gives this sequence:

Press On/Off to turn the water heater off.
Press and hold On/Off for 2 seconds, then press the Up button at the same time. The last nine codes flash one after another.
To exit, press and hold On/Off for 2 seconds, then the Up button at the same time.
Press On/Off to turn the water heater back on.

On linked systems of RU199, RU180, RU160, RU130, RUR, RSC or CU units, Rinnai’s note for these models says the primary controller flashes between SE and the set temperature while the secondary unit’s controller shows the actual code, so walk over to the second heater before you look anything up.

Codes 11 and 12: No Ignition, No Flame

These are the codes that leave you with a cold shower. Rinnai’s list for code 11 starts with the checks any owner can make:

Is the gas on? Look at the manual valve on the gas line just below the heater and at the meter. Our tip: if your stove or other gas appliances are out too, the problem is the supply, not the water heater — call your gas utility.
Propane: Rinnai says to make sure there is gas in the tank. Its technician guide adds that the tank must be properly sized for the application.
New installation or recent gas work: Rinnai lists bleeding air from the gas lines. That is gas-piping work for a licensed professional, not a homeowner job.

Past those checks, every item on Rinnai’s list is inside the cabinet: gas type and inlet pressure, the ground wire for the circuit board, the flame rod wire, the igniter, the gas solenoid valves and the gas orifice. Rinnai’s technician guide notes that loose flame rods or electrodes can lead to code 11 or 12, that a vent terminal without its required clearances can let exhaust recirculate and cause incomplete combustion, which leaves carbon on the flame rod, and it says in capitals not to adjust the internal gas valve. This is where the job belongs to a trained and qualified professional. Code 12 uses the same gas and flame-rod checks.

I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.

Code 10: Air, Exhaust or Condensate

Rinnai’s technician guide puts the condensate line first: if the drain line clogs or freezes, the water backs up into the trap inside the heater, which shuts itself off to prevent spillage and sets code 10. What you can check:

The condensate line — follow it to where it drains. Look for a kink, a clog or ice where it runs outside.
The vent terminal outside — the manual says to keep the area around the flue terminal free of snow and ice, and that the heater will not work properly if the air or exhaust pipes are blocked. Clear leaves, nests or snow you can reach safely. If the vent is blocked and cannot be easily cleared, Rinnai says to contact a trained and qualified professional.
The air filter (indoor units only) — see the next section.

The rest of Rinnai’s code 10 list — approved vent materials, vent length, the altitude setting, the fan wheel and the check valve between the fan and burner — is technician work. One item worth knowing about: the technician guide warns that spray foam around a vent pipe where it passes through a wall can collapse the pipe.

Cleaning the Air Filter and the Inlet Water Filter

These are the two filters Rinnai’s manual walks owners through. Air filter (indoor models):

Turn the heater off at the controller, then unplug it or switch off its breaker (the manual’s maintenance section says to cut the electrical supply before maintenance).
Remove the four screws that hold the front panel and lift it off. The filter sits in the upper right-hand corner; pull the tab marked “FILTER Pull to Clean.”
Scrub the filter area with mild dish soap and a soft-bristle brush, rinse with clean water and dry it with a lint-free towel. Repeat if it still looks dirty.
Put the filter back, refit the panel and restore power. Rinnai says not to run the heater without the air filter in place, and to call a trained and qualified professional for a replacement if the filter is damaged.

Inlet water filter (for “no code, nothing happens” and code 63): close the cold and hot isolation valves, put a bucket under the filter at the bottom of the heater, unscrew the filter, rinse the debris off, screw it back in and reopen the valves.

Code 14, SS and LC: Time to Flush

All three point at scale. Rinnai describes code 14 as a heat exchanger overheat and tells you to check for hot spots that indicate blockage from scale; SS is a time-based “Service Soon” reminder set during installation; and LC, on models with Lime Check, means the heater has detected calcium deposited inside the heat exchanger tubes. Rinnai says LC does not stop the heater at first, but that depending on the model it may lock the unit out.

The flush in Rinnai’s RU-series manual, in short:

It needs isolation valves with service ports on the hot and cold lines; Rinnai strongly recommends installing them.
Power off, close the shutoff valves, connect a pump hose to the cold-side service valve and a drain hose to the hot side.
Use four gallons of undiluted, food-grade white vinegar and circulate it for at least 1 hour at a rate of four gallons per minute.
Rinse with fresh water for five minutes, then remove and clean the in-line filter at the cold water inlet.
Reset SS afterward by pushing On/Off 5 times in 5 seconds.

Worth knowing: Rinnai says damage caused by lime build-up is not covered by the warranty, and that hard water must be treated to prevent scale. The same manual also says repairs and maintenance should be performed by a trained and qualified professional, so whether you flush it yourself or have it done is your call. If your heater has no isolation valves, adding them is a job for a licensed plumber.

The Flush Kit, If You Flush It Yourself

Superior Pump 91660 Tankless Water Heater Descaler Pump Kit. The listing says it includes a 1/6 HP pump, a 3.5-gallon pail with a screw-top lid, two 3/4-inch garden-hose-thread (GHT) stainless steel hoses 6 feet long and a 7 oz packet of descaler powder, and that it is designed to clean and descale most tankless water heaters. Rinnai calls for four gallons of vinegar, which is more than the kit’s 3.5-gallon pail holds, so run it from a 5-gallon bucket; the pump and hoses are the parts that matter. Rinnai’s manual specifies vinegar, so use vinegar rather than the included powder on a Rinnai unless your own manual says otherwise. It was shipped and sold by Amazon.com, new and in stock, when we checked on September 24, 2026; details come from the Amazon listing, not from hands-on testing.

For the full walk-through, including the isolation valves you need before any of this works, see how to descale a tankless water heater, and for the other kits we looked at, the best water heater flush kits.

When to Stop and Call a Licensed Professional

You smell gas. Leave the heater alone and follow the gas-smell steps at the top of this page.
Code 65. Rinnai says to turn off the water immediately, stop using the bath fill function and have a trained and qualified professional service the heater.
Code 16. It is a safety shutdown because the water got too hot; the fixes Rinnai lists are the fan motor and the gas valve assembly.
Any code whose fix is inside the cabinet — gas pressure, igniter, flame rod, sensors, fan, gas valve or circuit board.
The heater or its piping froze. Rinnai says not to operate it while frozen: close the gas and water valves, turn off the power, wait for it to thaw, then check the heater and piping for leaks before using it again.
Any part has been under water. Rinnai’s technician guide says not to use the heater.
Testing the pressure relief valve. Rinnai says this should only be done by a trained and qualified professional because the discharge can scald.

FAQ

How do I reset a Rinnai tankless error code?

Turn off every hot water tap first. Rinnai’s accessory instructions say most errors reset when the water flow stops or when the power is switched off and on, and for code 03 the manual says to press the ON/OFF button twice. If the same code comes straight back, the cause is still there and resetting again will not fix it.

What does code 11 mean on a Rinnai tankless water heater?

Code 11 is No Ignition. Rinnai’s first checks are that the gas is turned on at the water heater, the meter or the cylinder, and that a propane tank actually has gas in it. The remaining checks — gas pressure, air in the gas line, the igniter, the flame rod and the gas valve — are for a trained and qualified professional.

What does SS mean on a Rinnai?

SS means Service Soon. It is a time-based reminder, set during installation, that the heat exchanger is due to be flushed. Rinnai says to reset it by pushing the On/Off button on the temperature controller 5 times in 5 seconds, which you should do after the flush, not instead of it.

Can I clean the flame rod on my Rinnai myself?

We would not. Rinnai’s flame rod steps are in its technician troubleshooting guide, which says only trained and qualified professionals are permitted to follow it. The steps start with turning off the electrical, gas and water supply, and the igniter/flame rod gasket must be replaced if the seal is broken.

Why does my Rinnai show code 10 in cold weather?

Code 10 covers an air supply or exhaust blockage or a full condensate trap. Rinnai’s technician guide says a condensate drain line that clogs or freezes backs up into the trap inside the heater and shuts it off with a code 10, and the owner’s manual says to keep snow and ice off the vent terminal and the condensate line. Check both before anything else.

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Plumbing Picks is written by a Georgia journeyman plumber, and the license can be checked through the Georgia Secretary of State’s license verification portal. Every code meaning and step on this page comes from the manufacturer documents listed below, which we opened and read; where we add our own advice, the page says so. Product details come from the Amazon listing. Where a link goes to Amazon we may earn a commission at no extra cost to you. This page is general information for owners, not an offer of repair work. Nobody pays to be included here. More on who writes this and how we pick.

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Bottom Line

Read the code, write it down, and check the history before you reset anything. For 11 and 12, confirm the gas is on and the propane tank is not empty; for 10, look at the condensate line, the vent terminal and the air filter; for 14, SS and LC, the heat exchanger needs flushing. If the code comes back after those checks, or the fix is behind the front panel, it is a job for a trained and qualified professional.

Rinnai Tankless Error Codes: What Each Code Means