What does my water heater error code mean? Codes by brand

Before you look anything up

If you smell gas, ignore the code. Leave on foot, avoid anything that can spark, and call the gas utility and 911 from a safe place^[4].

Otherwise:

1. Write the code down exactly, including letters and any number that flashes before or after it.
2. Note the model number from the rating label. Some codes mean different things on different families within one brand.
3. Note what was happening: a cold snap, a power outage, the furnace running, a new install.
4. Do not reset more than once. One power cycle is a reasonable test.

Brand tables

Brand	Covers	Source document
Rinnai	SENSEI (RX, CX, RE, RSC), non-SENSEI (V, RL, RU, RUR, RUC), RH180 hybrid	Rinnai diagnostic code guide[1]
Navien	NPE-2 condensing tankless (A2 and S2 models)	Navien NPE-2 user's manual[2]
Rheem	Rheem and Ruud gas tankless, condensing and non-condensing	Rheem SVC820 pocket manual[3]

More brands, including A.O. Smith, Noritz, Takagi and the blinking status lights on gas tank heaters, are on our list to add.

The same fault across brands

Different makers, same problems. This cross-reference covers the faults behind most calls:

Fault	Rinnai[1]	Navien NPE-2[2]	Rheem[3]	Safe check
Burner will not light	11	E003	11	Gas valve open; other gas appliances work
Flame lost after lighting	12	E012	12	Confirm gas supply; note other appliances running
Vent or air blocked	10	E110	10, 90, 99	Clear outside terminals of snow, leaves, nests
Overheat	14	E016, E030, E046	14, 15	Stop resetting; call a pro
Condensate backup	25	n/a	29, 92, 93	Check the condensate line for clogs or ice
Scale or service due	LC, SS	E760	1L	Schedule a flush
Temperature sensor	32, 33, 51 and others	E407, E421, E432, E441	31 to 34	None: pro only
Fan or blower	61	E109	61, 79	Navien: clean intake air filter; otherwise pro
Circuit board or control	70	E515	82	One power cycle; then pro

Meanings are our paraphrase. Your model's manual is the final reference.

Myth: Navien E515 is the outlet temperature sensor

Several repair websites say so. Navien's own NPE-2 manual assigns the hot water outlet sensor to E407 and lists E515 as a main circuit board fault^[2]. Those are very different repairs at very different prices, so check the manual for your model before ordering parts.

What homeowners can safely check

The makers' documents limit owner checks to things that need no tools and no opening of sealed panels^[1][2][3]:

• Gas: the valve to the unit is open, the gas service is on, the propane tank is not empty.
• Power: the unit is plugged in and the breaker is on.
• Water: the cold supply valve is open; the inlet water filter is clean.
• Air (Navien): the intake air filter is clean.
• Vents: the outside intake and exhaust terminals are clear.
• Condensate: the drain line is not kinked, clogged or frozen.

What needs a licensed pro

Anything behind the front cover: gas valves and gas pressure, igniters and flame rods, temperature sensors, fans, circuit boards, heat exchangers, and venting changes. Overheat codes in particular should not be reset repeatedly; Rinnai says to treat its code 14 seriously^[1].

When to call a pro

• The same code returns after one reset.
• Any overheat, gas valve, sensor, fan or board code.
• A vent code that returns after the outside terminals are clear.
• A gas type mismatch code after an install or conversion (Navien E773 or E788^[2]).