Gas water heater pilot won't stay lit: thermocouple, thermopile and the status light

In A. O. Smith and State documents, the pilot flame of a gas tank water heater heats a thermocouple or a thermopile, and the gas valve stays open only while it does: when the flame is absent, the valve shuts off gas to both the pilot and the main burner (A. O. Smith 316877, p. 10; A. O. Smith 100263190, p. 21; State 186489, p. 23). The brands print different numbers for the same steps. Rheem and Bradford White labels ask for a five-minute wait before you light and State’s for ten, and an A. O. Smith service handbook says a cooling thermocouple can take up to 180 seconds to close the valve, a time that Rheem AP22543, AP23060 and AP22858 do not give (Rheem AP23060, p. 17; Bradford White 238-51012, p. 15; State 186489, p. 20; A. O. Smith 316877, p. 10).

How the pilot holds the gas valve open

Of the brands here, only A. O. Smith and State say in words what the thermocouple or thermopile does. Rheem’s AP22543, AP23060 and AP22858 say that the gas control “is constructed with a built in safety shut-off device designed to shut off the gas supply to the burner if the pilot flame is extinguished for any reason” and “is also equipped with a single use gas shut off device that will shut off the gas supply to the burner if the water heater exceeds normal operating temperatures” (Rheem AP22543, p. 18; Rheem AP23060, p. 19; Rheem AP22858, p. 18). Their “Before You Call For Service” tables name a thermocouple or a thermopile and a “Safety magnet” in the gas control and explain neither (Rheem AP22543, p. 21; Rheem AP23060, p. 22). Bradford White’s service manual tests the thermocouple, the thermopile and the magnet assembly with a meter without saying what they do (Bradford White 238-51542, pp. 15, 17, 21). A. O. Smith’s indexes tie its service handbooks 316877 and 327726 to Series 200/201 and Series 300/301, and its owner’s manuals 100263112 and 100263190 to ProLine Atmospheric Vent and ProLine Ultra Low NOx models (hotwater.com, service handbook and manual indexes).

Thermocouple

The Series 200/201 handbook, “intended for use by licensed plumbing professionals” (A. O. Smith 316877, p. 3), gives the chain: “The pilot flame heats the end of a thermocouple. As the thermocouple gets hotter, it generates a small (cannot be detected without an electrical meter) electrical current to the bottom of the gas control valve/thermostat. This current powers the electromagnet and holds open the main gas interrupter as long as the pilot flame is heating the thermocouple.” It adds: “If the pilot is extinguished, it can take up to 180 seconds for the thermocouple to cool sufficiently to close the safety valve.” (A. O. Smith 316877, p. 10).

The same handbook explains why you hold the knob in while lighting: “the flame must heat the thermocouple until it generates sufficient voltage to the gas valve to allow you to release the knob while gas continues to flow to the pilot.” (A. O. Smith 316877, p. 11). Rheem’s thermocouple bulletin sets the tip so that the pilot flame envelops its top 3/8 to 1/2 in. (Rheem bulletin 1410, p. 1).

1. Thermocouple tip in the pilot flame Rheem bulletin 1410, page 1: position the tip so that the pilot flame envelops its top 3/8 to 1/2 in.; then “Visually verify the thermocouple is enveloped in the pilot flame.” The bracket marks that length, not to scale.
2. Thermocouple line to the gas control A. O. Smith service handbook 316877, page 10: “As the thermocouple gets hotter, it generates a small … electrical current to the bottom of the gas control valve/thermostat.”
3. ECO probe in the tank water A. O. Smith service handbook 316877, page 11: “A metal tube (Temperature Probe) mounted onto the back of the gas control valve/thermostat is immersed inside the tank water.” The ECO switch is “within the probe”.
4. Thermal switch on the inner door Bradford White service manual 238-51542, page 6: “resettable thermal switch located on inner door”. The outer door is left off the drawing.
5. Flame arrestor State 186489, page 7: the FVIR system traps “the burning vapors within the water heater combustion chamber through the special flame-arrestor.”
6. Base-ring filter State 186489, page 27: check the base-ring filter “for any dust or debris that may have accumulated on the filter screen.”

Thermopile

The Honeywell valve in the Series 300/301 handbook “uses a thermopile instead of a thermocouple as did previous designs.” Its voltage “opens the power head in the control, allowing gas to flow. It also powers the onboard diagnostics (status light).” (A. O. Smith 327726, p. 7). Warming the thermopile “may take up to 90 seconds of continuous pilot operation” before the light blinks (A. O. Smith 327726, p. 10). The labels of Rheem and Bradford White, written for their own status light valves, have you hold the knob until the light blinks and print no hold time: Rheem’s 90 seconds is the point to start over when the light has not blinked and the pilot is not lit, and the Bradford White Resideo label adds “It can take up to 15 seconds for gas to begin flowing after the pilot is lit.” (Rheem AP23060, p. 17; Bradford White 238-51012, pp. 16, 17).

Rheem’s AP23060, A. O. Smith’s two ProLine owner’s manuals and Bradford White’s ICON labels pair the status light with a thermopile (Rheem AP23060, p. 24; A. O. Smith 100263112, p. 27; A. O. Smith 100263190, p. 21; Bradford White 238-51012, p. 16). Rheem’s AP22858 prints both words, “Loose thermocouple.” in one table and “Check thermopile connector” in another, and does not say which applies (Rheem AP22858, pp. 21, 23).

1. Knob at the pilot position and pressed in: gas flows to the pilot burner only

2. Piezo igniter lights the pilot

3. Pilot flame heats the end of the thermocouple; it sends a small current to the gas control valve/thermostatNormal: 20 to 30 mV

4. The current powers the electromagnet, which holds the main gas interrupter open; with enough voltage, the knob can be released

5. Knob at ON: gas also reaches the main burner when the thermostat calls for heat

   Water excessively hot: the ECO in the temperature probe opens and interrupts the current. Not resettable: the entire control is replaced

6. Pilot goes out: up to 180 seconds for the thermocouple to cool and close the safety valve

The handbook does not tie the ECO or a pilot outage to a step; both are drawn after the knob is at ON.

1. Pilot lit; the control knob is held in until the status light blinksUp to 90 seconds of continuous pilot operation before the light starts to blink

   Lit 90 seconds, still no blink: thermopile connections may be loose, the thermal switch may need a reset, or the thermopile may be defective

2. Heat on the thermopile: 750 to 900 mV, open circuit

3. Connected to the control: at least 350 mV, closed circuit. The voltage opens the power head, gas flows, and it powers the status light

4. Status light: 1 flash, normal operation, a bright/dim heartbeat

   Water too hot: the ECO shuts off the main burner and pilot; once relit, the light flashes 4

5. Pilot goes out: status light on solid while the thermopile cools; knob to OFF, wait 10 minutes, then relight

The 90-second check is on page 9, the light states on page 10, the ECO on page 7. The handbook does not tie the ECO or a pilot outage to a step.

Thermocouple vs. thermopile, by document

Document	Part	What it does, as printed	Voltage printed
A. O. Smith handbook 316877, Series 200/201 (A. O. Smith 316877, pp. 10, 20)	Thermocouple	“powers the electromagnet and holds open the main gas interrupter”	Normal “between 20 and 30 mv”; test after 45 seconds: “20-30 millivolts DC or more”
State 186489 (State 186489, pp. 23, 31)	Thermocouple	“used to determine if a pilot flame is present”	Test after 45 seconds: “12 millivolts DC or more”
Bradford White, White Rodgers mechanical control (Bradford White 238-51542, pp. 15, 16, 21)	Thermocouple, magnet assembly	Not explained	Closed circuit: “10 millivolts or higher”; open circuit: “20 to 30 millivolts”; the magnet should stay closed “for a drop of at least 6 millivolts”
A. O. Smith handbook 327726, Series 300/301 (A. O. Smith 327726, pp. 7, 10)	Thermopile	“opens the power head in the control, allowing gas to flow”; powers the status light	“750 to 900 millivolts (open circuit)”; “at least 350 millivolts (closed circuit)”; below 350 millivolts DC, replace the thermopile
A. O. Smith 100263190 and 100263112 (A. O. Smith 100263190, p. 21; A. O. Smith 100263112, p. 27)	Thermopile	100263190: “used to determine if a pilot flame is present”; 100263112: not explained	None
Bradford White, Resideo and White Rodgers electronic controls (Bradford White 238-51542, p. 17)	Thermopile	Not explained	“between 350mV - 850mV”, open circuit, with the red wire off the thermal switch
Rheem AP22543, AP23060, AP22858 (Rheem AP22543, p. 21; Rheem AP23060, pp. 22, 24; Rheem AP22858, pp. 21, 23)	AP22543 thermocouple, AP23060 thermopile, AP22858 both words; “Safety magnet” in all three	Not explained; the gas control’s built-in pilot-out shut-off device is described in words (AP22543, p. 18; AP23060, p. 19; AP22858, p. 18)	None; AP23060 says “millivoltage” with no value

Keep each number with its document: State’s owner’s manual and A. O. Smith’s 316877 describe the same thermocouple test and ask for 12 and for 20-30 millivolts DC or more (State 186489, p. 31; A. O. Smith 316877, p. 20). The other numbers come from service documents; the cover of 327726 reads “FOR USE BY QUALIFIED SERVICE PROFESSIONALS ONLY”. Our advice: leave meter tests on the gas control to a technician.

Lighting the pilot by the label

Use the label on your own heater; Rheem’s status light table and A. O. Smith’s chart both send you to the lighting instructions on the water heater (Rheem AP23060, p. 24; A. O. Smith 100263112, p. 27).

Label (document)	Valve	Wait before lighting	Hold	Repeat
Rheem AP22543 (Rheem AP22543, p. 16)	Thermocouple	“Wait five (5) minutes to clear out any gas.”	Knob, “for about one (1) minute after the pilot is lit”	“repeat steps 3 to 9”; the wait is step 4
Rheem AP23060, AP22858 (Rheem AP23060, p. 17; Rheem AP22858, p. 16)	Status light	Five minutes	Knob, “until the “STATUS” indicator light begins to blink”	No blink after 90 seconds and no pilot: “repeat steps 2 through 6”; the wait is step 3
State 186489, White-Rodgers valve (State 186489, p. 20)	Thermocouple	“Wait ten (10) minutes to clear out any gas.”	Knob, “for about one (1) minute after the pilot is lit”	“repeat step (3) through (9)”; the wait is step 5
State 186489, Robertshaw valve (State 186489, p. 21)	Thermocouple, reset button	Ten minutes	Reset button, “for about (1) minute after the pilot is lit”	“repeat steps 3 - 7”; the wait is step 5
A. O. Smith 100263112, steps in the manual (A. O. Smith 100263112, p. 23)	Status light	None before the first try; the heater’s own label is not reproduced	Knob held in, igniter clicked “for up to 90 seconds or until the Status Light starts to flash”	“Wait 10 minutes between lighting attempts.”; three attempts in all
A. O. Smith 100263190, label (A. O. Smith 100263190, p. 18)	Status light	“Wait ten (10) minutes to clear out any gas.”	Knob held in, igniter clicked “for up to 90 seconds or until Status Light begins to blink”	“up to THREE (3) times, waiting 10 minutes between lighting attempts”
Bradford White, White Rodgers mechanical (Bradford White 238-51012, p. 15)	Thermocouple	“Wait five (5) minutes to clear out any gas.”	Button or knob, “for about one (1) minute after the pilot is lit”	“repeat steps 3 through 9”; the wait is step 4
Bradford White ICON, SIT and Resideo (Bradford White 238-51012, pp. 16, 17)	Status light	Five minutes	Knob, “until the status light blinks”; Resideo: “It can take up to 15 seconds for gas to begin flowing after the pilot is lit.”	SIT “repeat steps 2 through 8”, Resideo “repeat steps 2 through 7”; the wait is step 3

A. O. Smith’s flue damper manual 100400765 says “The water heater will light automatically. DO NOT try to light the pilot by hand.” (A. O. Smith 100400765, p. 22). On the page before its labels Bradford White prints “Wait at least 2 minutes after this control is pressurized with gas before attempting to light pilot and/or push igniter button.”, without saying which controls it means (Bradford White 238-51012, p. 14). A. O. Smith’s ULN guide explains its ten minutes between tries: “The circuitry in this gas valve requires that you wait 10 minutes between lighting attempts.” (A. O. Smith 100263190, p. 17).

When to stop and call

The Rheem, State and Bradford White labels above share two stop rules (Rheem AP22543, p. 16; Rheem AP23060, p. 17; State 186489, pp. 20, 21; Bradford White 238-51012, pp. 15, 16, 17):

• If the knob or button does not pop back up when released, stop and immediately call your service technician or gas supplier. State’s Robertshaw label says to “immediately shut off the gas at the line valve or tank” first.
• If the pilot will not stay lit after several tries, turn the knob to OFF and call your service technician or gas supplier.

A. O. Smith counts the tries: after three attempts the knob goes to OFF. The ULN label then says to call “a qualified service technician or your gas supplier” (A. O. Smith 100263190, p. 18). The ProLine Atmospheric Vent manual sends you to its no-hot-water steps, a spark and gas valve check that ends with “If the pilot still does not light, call a qualified person.” (A. O. Smith 100263112, pp. 23, 25). If you smell gas, do not light anything; see If you smell gas.

What the status light says

Not every gas tank has one. Rheem’s AP22543 and State’s 186489 describe thermocouple valves with no light, though State’s GSX-40-BCTL 410 product page, which lists 186489 as its manual, advertises an “LED status indicator” (statewaterheaters.com, GSX-40-BCTL 410). Check the gas control on your own heater.

The pilot must be lit for a code to show. If it goes out when you let go of the knob, Rheem says to relight and “keep the knob depressed until the pilot is lit and the status light code can be fully read”; its legend shows the normal blink in blue and the fault codes in red (Rheem AP23060, p. 24).

Light	Rheem AP23060, AP22858 (Rheem AP23060, p. 24; Rheem AP22858, p. 23)	A. O. Smith 100263112 (A. O. Smith 100263112, pp. 23, 25, 27)	Bradford White Resideo V1; V2 and SIT (Bradford White 238-51012, pp. 23, 24)
Off	Control off, pilot not lit, or “Insufficient power supply (millivoltage)”. Status light off	“Pilot light is not lit. Not enough power (millivolts) to keep it lit.”	V1: “Millivolt power is not present. Light pilot.” V2, SIT: control in OFF mode, pilot off
On, steady	“Pilot recently extinguished and Thermopile is cooling down”, or the knob was recently turned to OFF; light the pilot; no minutes printed. Status light steady	“A solid Status Light means the pilot was lit but is now off.”; release the knob, wait 10 minutes, relight once the light goes out	V1: knob recently turned to OFF, “Wait until LED goes out before attempting to relight.” V2, SIT: shutdown mode, pilot off; wait until the LED turns off
1	Every three seconds: “Normal Operation”, blue. 1 blink	Every three seconds: pilot lit, no problems detected	V1: “One flash and three second pause”, pilot flame detected with the knob at PILOT; two quick flashes on a call for heat. V2, SIT: every four seconds, pilot lit and burner off; every second, burner lit
2	“Low thermopile voltage however pilot is lit”. 2 blinks	Low millivolts: check the wiring, then “Replace the thermopile.”	V1: “Weak pilot flame detected. System will reset when pilot flame is sufficient.” V2: “Low thermopile voltage; main valve not turned ON.”
4	“High water temperature limit tripped”; “Contact a qualified service technician.” 4 blinks	“High water temperature has activated the over heat sensor.”; “Replace the gas control valve/thermostat.”	V1: “Excessive tank temperature. System must be reset.” V2: “Temperature cut-out limit reached, causing shutdown.”
5, 7, 8 and more	Water temperature sensor failure, gas control failure, false pilot flame signal; for each, contact a qualified service technician. AP22858 adds 9 and 10, chamber faults. 5 blinks, 7 blinks, 8 blinks, 9 blinks	5, 7: replace the valve. 8: a pilot flame with the knob at OFF means the pilot valve is stuck open: turn the main gas supply OFF and replace the valve; no flame: wait 10 minutes, relight, and replace the valve if the code returns. The ULN guide adds 9 and 10 (A. O. Smith 100263190, p. 21)	V1, 7 and 8: valve fault, false pilot flame; for 7, first check that the control is not wet or damaged; for both, knob to OFF, then PILOT and relight; replace the gas valve if the code persists

3 sflash length not printed

4 sflash length not printed

1 sflash length not printed

One flash means different things on different valves, as the Bradford White column shows; A. O. Smith’s 327726 calls normal operation a “bright/dim heartbeat” (A. O. Smith 327726, p. 10). Bradford White’s quick service guide splits its ICON control at serial date code TA, January 2019, and ICON 2.0 has no seven- or eight-flash codes (Bradford White quick guide, PDF pp. 1, 2); none of the three Bradford White documents here matches ICON 1.0 and 2.0 to the V1, V2 and SIT of the I&O manual. Rheem’s and A. O. Smith’s tables share the counts 0, 1, 2, 4, 5, 7 and 8, but Rheem does not name the maker of its gas control, and the remedies differ (Rheem AP23060, p. 24; A. O. Smith 100263112, p. 27). Read the table in your own manual.

FVIR, the thermal switch and the ECO

FVIR, the Flammable Vapor Ignition Resistance system, “is designed to reduce the risk of flammable vapor-related fires” and “makes this product more sensitive to installation errors or improper installation environments” (A. O. Smith 100263112, p. 5). After a flammable vapor incident it “disables the water heater by shutting off the gas supply to the water heater’s burner and pilot” (State 186489, p. 7). A. O. Smith and State print its limit in the same words: it “will not prevent a possible fire/explosion if the igniter is depressed and flammable vapors have accumulated in the combustion chamber with the pilot light off.” (A. O. Smith 100263112, p. 5; State 186489, p. 7).

The thermal switch (TCO) shuts off the gas on high combustion chamber temperatures from “flammable vapors (e.g. spilled gasoline), poor combustion caused by a blocked vent or insufficient combustion air” (A. O. Smith 316877, p. 11); a trip “is most likely caused by poor combustion (e.g., blocked vent or dirty filter/arrestor)” (A. O. Smith 327726, p. 8).

The ECO limits water temperature. In 316877 it opens when the water gets excessively hot, interrupting “the small electrical current to the gas valve”; “The ECO is NOT resettable.”, and the entire control is replaced (A. O. Smith 316877, p. 11). State sets its ECO at 195°F (91°C) and calls it “a single-use switch” (State 186489, p. 23); A. O. Smith’s ULN guide gives 189°F (87°C) (A. O. Smith 100263190, p. 22). Rheem prints neither “ECO” nor “thermal switch”. Its three manuals say the gas control has “a single use gas shut off device that will shut off the gas supply to the burner if the water heater exceeds normal operating temperatures” (Rheem AP22543, p. 18; Rheem AP23060, p. 19; Rheem AP22858, p. 18) and describe a “combustion shut off device” that stops the heater on “the presence of flammable vapors or blockage of the combustion air inlet openings” (Rheem AP23060, p. 22).

Who resets a safety shutoff

Document	Device	Reset printed	For whom
Rheem AP22543, AP23060, AP22858 (Rheem AP23060, p. 22)	Combustion shut off device	None; the word reset does not appear in these manuals	“Please contact a Qualified Service Technician if this occurs.”
Rheem AP22543, AP23060, AP22858 (Rheem AP22543, pp. 18, 21; Rheem AP23060, pp. 19, 22)	Single use gas shut-off device in the gas control	None; the table says the gas control “should be replaced by a qualified service technician”	Qualified service technician
A. O. Smith 100263112 (A. O. Smith 100263112, p. 5)	“resettable thermal switch”	None	Not stated; “Do not attempt to disable or modify this feature in any way.”
A. O. Smith 100263190 (A. O. Smith 100263190, p. 22)	Combustion chamber temperature sensor; the reset is for the gas control	Knob to OFF, unplug the thermopile plug, wait about three minutes, plug it back in, knob to PILOT and restart; first, “Correct any issues prior to resetting the gas control valve/thermostat.”	Owner’s guide
State 186489 (State 186489, p. 23)	Thermal switch	Check the flame arrestor for blue or black discoloration; if there are signs of high temperature, inspect the venting, the combustion air supply and for a flammable vapor event; “Correct any issues prior to resetting the thermal switch.”; then press the small button in its center	Owner’s manual; a suspected flammable vapor incident goes to a qualified technician
A. O. Smith handbooks 316877, 327726 (A. O. Smith 316877, p. 20; A. O. Smith 327726, pp. 8, 10)	TCO	316877: “press the TCO reset button”. 327726 puts the button “in its center” and says to “determine the cause and correct it before returning the water heater to service”	Service professionals
Bradford White (Bradford White 238-51012, p. 2; Bradford White 238-51542, p. 37)	“Re-settable Thermal Switch”	I&O manual: none. Service manual: press the red button at its center; “The overheating condition must be determined prior to putting the heater back in service.”	Qualified service providers

State also says FVIR service “should only be performed by a qualified technician” (State 186489, p. 6). Do not apply one series’ reset to another. Our advice: if your manual gives the owner no reset step, leave the switch to a qualified service technician.

After a flammable vapor incident, A. O. Smith, State and Bradford White require replacement of the whole water heater (A. O. Smith 100263112, p. 5; State 186489, p. 23; Bradford White 238-51542, p. 37), and Bradford White’s limited warranty does not cover that replacement (Bradford White 238-51012, p. 2). Rheem: the heater will not ignite “until examined by a Qualified Service Technician” (Rheem AP23060, p. 7). In A. O. Smith 100400765, seven flashes is a “Flammable Vapor Sensor (FVS) Lockout” (A. O. Smith 100400765, p. 28).

Why the pilot goes out, in the manufacturers’ words

The lists differ by brand. Bradford White separates a pilot that “will not stay lit when button is released”, with seven causes in the thermocouple, the ECO, the magnet and the thermal switch, from one that “goes out periodically (after heating cycles, once a day, once a week etc.)”, with three: combustion air, the vent and the gas supply (Bradford White 238-51542, pp. 6, 7).

Document	Causes, as printed	Who acts
Rheem AP22543, AP23060 (Rheem AP22543, p. 21; Rheem AP23060, p. 22)	Thermocouple loose or defective (AP22543), thermopile disconnected or defective (AP23060), “Safety magnet defective.”, the gas control’s “single use gas shut-off device has opened.”, “Combustion Shutoff Device Tripped.”; both also print, in the Condensation row: “Excessive condensation can cause pilot burner outage.”	A qualified service technician; AP23060’s check of the thermopile wire connectors names no one
Rheem bulletin 1411 (Rheem bulletin 1411, p. 1)	Summer attic heat from “Poor attic ventilation” on standing pilot heaters	“The only resolution is to increase attic venting.”
Rheem TB-1443 (Rheem TB-1443, PDF p. 1)	ULN atmospheric models “in limited production quantities”: “Pilot assembly out of position”	Not stated
A. O. Smith 100263112 (A. O. Smith 100263112, pp. 23, 29)	“If the air filter is not cleaned as needed, the water heater’s pilot may go out.”	The owner inspects and vacuums the filter at least annually
A. O. Smith 327726 (A. O. Smith 327726, pp. 15, 23, 24)	“Elevated air temperature”, “Insufficient makeup air”, “Blocked air screen or flame arrestor”, “Improper venting of the water heater”, “Decompression”, “Wind”; condensation “On some models”	Attics: “Contact a licensed contractor or a roofing professional for guidance.”
State 186489 (State 186489, pp. 23, 29)	15 causes, among them the thermal switch tripped, a loose thermocouple connection, low gas pressure, cold drafts, the ECO switch open, air for combustion obstructed and the base-ring filter obstructed; also excessive condensation	A remedy for each, from tightening the thermocouple to “Check with gas utility company” and “Replace water heater”
Bradford White 238-51542 (Bradford White 238-51542, pp. 6, 7)	Thermocouple connection or seating, flame not enveloping the bulb, weak thermocouple, open ECO, defective magnet, opened thermal switch; for periodic outages, combustion air, the vent and “Inconsistent gas supply or gas pressure.”	Service manual for qualified service providers

A. O. Smith’s handbook explains the attic case: “when the pilot flame consumes the oxygen in the sealed combustion chamber and that oxygen isn’t replaced by a proper draft, the flame will go out.” (A. O. Smith 327726, p. 24). Indoors, “a classic decompression condition can be caused by a large kitchen exhaust fan” (A. O. Smith 327726, p. 25). Without sufficient air, it adds, a water heater “will have frequent pilot outages and may emit excessive and abnormal amounts of carbon monoxide” (A. O. Smith 327726, p. 21). Closet air openings are on the water heater closet page.

In winter, State and A. O. Smith place condensation in “the winter and early spring months when incoming water temperatures are at their lowest”. State says water running down the flue tube onto the main burner can put out the pilot (State 186489, p. 23); A. O. Smith says condensation may cause 2 flashes, low thermopile voltage, which “may clear up as the tank begins to warm” (A. O. Smith 327726, p. 15). Before the season, see the winter checklist.

What an owner can check, and what is technician work

The owner’s part in these manuals:

• Look at the pilot and relight it by the label if it is out: “Visually inspect pilot burner and relight if necessary.” (Rheem AP22543, p. 19).
• Read the status light with the pilot lit and “record any diagnostic codes” (A. O. Smith 100263112, p. 27).
• If an A. O. Smith ProLine Atmospheric Vent will not light, “Dim the room lights and look through the viewport while clicking the igniter button.” With no spark, check that the igniter wire is firmly in its white connector; with a spark, make sure the gas supply valve is on (A. O. Smith 100263112, p. 25).
• Keep the combustion air inlets open; in a closet, Rheem asks for at least 1 in. between them and any obstruction (Rheem AP23060, p. 8).
• Vacuum the air filter at least once a year if your manual gives you that job, as A. O. Smith’s ProLine Atmospheric Vent manual does (A. O. Smith 100263112, p. 29). State describes the same for its base-ring filter after a note that FVIR maintenance “should be performed by a qualified technician” (State 186489, pp. 25, 27); Bradford White gives clearing the jacket slots to “a qualified service technician” (Bradford White 238-51012, p. 21).
• Keep gasoline and other flammable liquids away from the heater (A. O. Smith 100263112, cover, PDF p. 1; State 186489, p. 1). A. O. Smith’s carbon monoxide warning says: “Install a fuel gas and carbon monoxide detector in the living areas of your home.” (A. O. Smith 100263112, p. 6).

The rest is service work. Rheem: “DO NOT attempt repair of gas piping, Combination Gas Control (Thermostat), burners, vent connectors or other safety devices. Refer repairs to qualified service personnel.” (Rheem AP23060, p. 22). Bradford White: “do not attempt repair of combination gas control, burners or gas piping. Refer repairs to a qualified service technician.” (Bradford White 238-51012, p. 22). State gives examples of a qualified technician: “licensed plumbers, authorized gas company personnel, and authorized service personnel” (State 186489, p. 6). A. O. Smith’s ProLine Atmospheric Vent chart says “Replace the gas control valve/thermostat.” for 4, 5 and 7 flashes without naming anyone, and its cover says “Installation and service must be performed by a qualified installer, service agency or the gas supplier.” (A. O. Smith 100263112, p. 27; A. O. Smith 100263112, cover, PDF p. 1). Read that replacement as service work.

Some causes lie outside the heater: for low gas pressure or no gas, State says “Check with gas utility company” (State 186489, p. 29), and for attic heat A. O. Smith points to “a licensed contractor or a roofing professional” (A. O. Smith 327726, p. 24). Rheem’s consumer article on when to call a plumber includes a pilot light that won’t stay lit: “A plumber can safely get to the root of the cause and fix this for you.” (Rheem, “7 Signs You Need to Call a Plumber”, September 1, 2020). Our advice: once the label’s tries are used up, call a licensed plumber or gas service technician.

If you smell gas

Do not light the pilot, and follow the safety box on this page, which quotes Rheem’s cover. The covers differ: A. O. Smith and State print four points, without “Do not return to your home until authorized by the gas supplier or fire department.”; Bradford White prints five, with the electrical switch and the phone as separate points and none about returning home (A. O. Smith 100263112, cover, PDF p. 1; State 186489, p. 1; Bradford White 238-51012, cover, PDF p. 1). Rheem adds “Leave the house immediately and make sure your family and pets leave also.” and warns that LP gas “is heavier than air and will collect first in lower areas making it hard to detect at nose level.” (Rheem AP23060, p. 5). Bradford White’s labels ask you to smell for gas “including near the floor” before you light (Bradford White 238-51012, p. 15), and for flammable vapors say “Leave the premises and immediately call the fire department from a neighbor’s phone.” (Bradford White 238-51012, p. 2).

Related pages on this site

• Rheem, Ruud and Richmond status light codes: status light off, status light steady, 1 blink, 2 blinks, 4 blinks, 5 blinks, 7 blinks, 8 blinks, 9 blinks. Power vent and induced draft tanks use a gas valve LED with other counts, listed on the Rheem gas tank code hub.
• Closets and alcoves: Water heater or furnace closet: clearance and air requirements.
• Before the heating season: Winter home maintenance checklist.
• Tankless heaters: How a tankless water heater lights: ignition codes by brand.

What these documents do not cover

• Rheem AP22543, AP23060 and AP22858 do not explain the thermocouple, the thermopile or the safety magnet, and print no millivolt values, no time for the valve to close and no reset steps.
• Which control a heater has. State’s GSX-40-BCTL 410 page advertises a status light and lists a 2008 manual for a thermocouple valve; Bradford White’s ICON names are tied to each other only by a serial date; A. O. Smith’s 100263112 does not reproduce the heater’s label. The label on your own heater decides.
• Dates. State 186489 is printed “0808”, A. O. Smith 100263112 and 100263190 are dated January 2015, and the makers’ sites list them for ProLine models; none says which serial numbers it covers.
• Not read for this page: Rheem AP23059 and other Rheem and Ruud series, A. O. Smith High Recovery models, Bradford White damper and high-input models, Reliance and other brands, power vent and direct vent tanks.
• This page leaves out gas pressure values, vent sizing, attic ventilation amounts and carbon monoxide levels, although some of these documents print gas pressures and attic ventilation figures (for example A. O. Smith 327726, pp. 7, 24).

See also

• Water heater size calculator
• 2029 water heater regulations: the DOE standard from May 6, 2029
• Furnace and HVAC tax credits for 2025 and 2026: 25C ended after 2025
• Form 5695 for 2025 and 2026: QMID, lines, carryforward
• Home maintenance schedule from the manuals: monthly to yearly
• Winter home maintenance checklist: furnace, boiler, water heater
• Water heater or furnace closet: clearance and air requirements

Error codes: Rheem gas tank water heaters