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How to troubleshoot gas water heater
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Basics
Emergency? Leave house if you smell gas.
Do not turn on light switch or touch any light switch or electrical device that might cause static spark
Turn off gas
When gas handle is perpendicular across gas line, then gas is OFF

Resources
Emergency steps for leaking water heater
Troubleshoot leaking water heater
Flooded water heater
How to light gas water heater
Not enough hot water? IF water inside tank is hot, then plumbing is suspect.
Open drain valve and check if water is hot
Resources:
Low hot water pressure
Crossover
Broken pipe or leaks running hot out of tank
Hot water connected to toilet or outdoor spigot
Mixing valve is broken
Other valves not functioning
Recirculation system needed or not functioning
IF water is not hot, then water heater is suspect.
Open drain valve and check if water is hot

Resources:
Test gas valve thermostat
Broken dip tube
Undersized water heater
Other reasons are covered on this page
Water too hot? Water too hot?
Troubleshoot gas control thermostat
Stacking
Common water heater problems Common water heater problems:
Low hot water pressure
Stacking
Crossover
Flooded water heater
Leaking water heater
General how-to
Find age of water heater
How to replace drain valve
How to read the gas meter
Clean sediment out of tank and periodic flushing
How to install electric water heater
Thermal expansion tank
Noisy-gas-water-heater
Tank water heater forum
Water too cold? Open drain valve and see if tank has hot water
If water inside tank is hot, then check for water leak somewhere. Check for crossover
Crossover
If water inside tank is cold, then check for water leak somewhere. Troubleshoot thermostat
Troubleshoot gas control thermostat
New water heater? How to install gas water heater
Which is best gas water heater
Solar Heat with solar
Connect PV water heater / low voltage
Connect PV water heater / high voltage
Prevent problems
Maintain water heater to last years beyond warranty.
How to maintain water heater
    1)  Read about anode rods
    2)  Read about stray current corrosion
    3)  How to flush water heater
    4) Inspect for leaks
    5)  9 ways to save with water heater
    6) Water heater safety precautions
    7) Repair water heater valves
    7) Read manual and follow maintenance schedule
Gas water heater parts  
Larger image
Basic parts
Gas water heaters are not 100% standardized. Models vary.  Manufacturers offer different designs.
Parts not shown on illustration include: Electronic gas control valve, power vent, flue damper vent, FV sensor, flexible gas line, air intake, thermocouple, thermopile, pilot etc.

Resources
TP valve code
Replace TP valve
Repair water heater valves
Remove short water heater nipple
Broken dip tube
Replace drain valve
Index of all plumbing links
Install gas water heater
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Honeywell gas control
Electronic controls have thermopile instead of thermocouple
Larger image
Basic gas valve thermostat parts
Gas water heaters have a control valve with a probe that extends into water heater to measure temperature.
Replacement
Troubleshoot gas control valve thermostat
How to replace water heater gas valve
How to light gas water heater

Buy:

Gas water heater thermostats Amazon
AO Smith gas valves at Amazon

Buy:

AO Smith gas water heater at Amazon
Bradford White gas water heater
Rheem gas water heater at Amazon

Mechanical control thermostats have thermocouple
Larger image
10 things needed for gas water heater
What you need for operation of gas water heater.
This page contains information for each item with .pdf resources
1) Adequate incoming air supply ... issues: closed doors, tightly insulated house, very hot attic.
2) Adequate air supply getting to burner... issues: dirty vent screen, dirty environment, maintenance.
3) Thermal cutoff  ... TCO ... issues: failed part, maintenance, vent.

4) Flammable vapor lockout .... issues: exposure to vapors, bad FV sensor, failed FV system,
5) Fuel supply... natural gas and propane are different ... issues: wrong gas, low pressure, moisture in pipe.
6) Gas valve thermostat regulates fuel supply ... issues: not enough gas, failed thermostat, failed gas control valve.

7) Fuel supply to burner ... issues: maintenance, thermocouple-thermopile, gas control valve.
8) Functioning thermopile-thermocouple-pilot light ... issues: misalignment, failure of part.
9) Ignition of fuel supply by pilot light or hot surface igniter ... issues: pilot light, piezo igniter, electrode.

10) Power vent models ... issues: pressure switch, blower, blower sequence from gas control, polarity
11) Venting of combustion byproduct .... issues: vent in disrepair, other vents in house drawing air
Troubleshoot starts here

Bradford White air intake shown
Buy:
Bradford White water heaters
Back to 10 things for troubleshooting water heater
1) Incoming air supply
Water heater must have enough air to support combustion.

Well-insulated house or closed doors can prevent adequate air from reaching water heater.
Very hot attic will cause oxygen molecules to spread too far apart to support combustion.

AO Smith and 3-legged water heaters have air intake located on bottom of heater (install heater on 3 bricks to elevate space under heater), Bradford White (pictured) has air intake on side.
Solution:
Do not install gas water heater in small contained area, use louvered doors, do not pile belongings around water heater. Get fresh air to water heater and see if problem is resolved.
close up water heater air intake
AO Smith air intake on bottom of heater shown
Back to 10 things for troubleshooting water heater
2) Air supply getting to burner
Air intake must be clean. If intake is blocked, the combustion flame is yellow and lazy instead of crisp and blue. Water heater might not stay lit.
See manual for location of air intake.
Do not install water heater in dusty environment.
Avoid dusty environment that will clog air intake, cause unburned fuel, and create fire hazard.
Some FV designs can trip if the air intake is clogged.



Dirty, dusty and chemical environments pose hazards for all gas appliances. Water heaters air intake will clog, and shut down burner or cause FV lockout in some models.
Whirlpool shown.

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Location of AO Smith/ American/ Kenmore/Whirlpool 3-legged water heater with arrestor screen that will clog with dust. 
Flame trap inspection
Inspect and Clean air intake on AO Smith, State, American, Reliance, Whirlpool water heaters using feather duster or compressed air.
Buy:
Flame trap inspection mirror at Amazon
Rheem, Richmond, Ruud, GE heaters require removal of combustion parts to clean arrestor screen located inside unit.
Remove combustion parts for maintenance.

Buy:
Flame trap inspection mirror at Amazon
Flame should burn clear blue
Lazy yellow flame indicates one or more of following:
-Poor incoming air supply.
-Inadequate venting.
-Dirty combustion parts.
-Low gas pressure
Ventilate attic
Very hot attic causes oxygen molecules to spread too far apart to support pilot light.
Increase ventilation to water heater
Resource:
Attic ventilation/ pilot outage pdf
Whirlpool ECO thermal switch
Buy:
Thermal reset
Back to 10 things for troubleshooting water heater
3) Thermal cutoff  ... TCO
Located on front of combustion chamber near the sight glass, with two wires that connect to gas control valve.
Thermal cutoff trips when combustion chamber get too hot. Prevents overheating and is part of the FV system: 
Push inward to reset, or replace part as needed.
Tripped TCO stops all gas from reaching the pilot light or the burner... it causes a complete shut down of gas control valve, and no gas reaches the combustion chamber. If there is a pilot light burning, or flutter of gas on the burner, the TCO is not tripped, and gas control valve is suspect.
Causes of tripped TCO are dirty combustion parts, clogged vent... these things cause overheated combustion chamber.
Solution: Push in button to reset, replace TCO, clean burner parts, check vent is drafting air.
Buy:
Thermal reset


Buy:
Flammable sensor kit
Back to 10 things for troubleshooting water heater
4) Flammable vapor sensor/ variety of systems
Primary issue for FV is exposure to explosive flammable vapors that can be drawn into combustion flame, causing flashover that travels from inside the water heater and accelerates back into surrounding room. This potentially deadly situation has caused fatalities, injury and property loss. Flammable vapors are commonly found in oil paint, shellac, varnish, adhesives, gasoline. Turn off all pilot lights when working with flammable materials. Do not store flammables in same area as water heater.
FV lockout reduces risk of fire either by turning off gas control valve or limiting exit of flame from combustion chamber.
Some water heaters have external vapor sensor (shown in illustration on left), and some have internal FV system (shown below), or both.
External vapor sensor can be seen attached to front of water heater, near the bottom as pictured on left.
With this type FV sensor: If water heater has no gas, then FV is suspect: test and replace part. If water heater has some gas but flame flutters out then internal FV might be suspect, or air intake clogged ... keep reading and then check #6 gas control valve plus #7 #8 #9.
How the external FV sensor operates: Two wires connect the vapor sensor to the gas control valve, the sensor 'shorts out' when exposed to gasoline vapors, and shuts down gas valve during vapor event.
Buy:
Flammable sensor kit
Resource:
How FV sensor works
How to test FV sensor
American FVIR bulletin
FVIR troubleshoot guide
FV sensor If flammables materials are used, then all gas burning appliances in the vicinity must be shut off and pilot lights extinguished. Open doors and windows for ventilation while flammable substances are in use.
The FV sensor is located inside a plastic case to keep it dry and clean... if the sensor is blocked, or has been covered with dust, leaves, water etc, it will not function. Replace part.
The FV sensor must have continuity, so a small current of electricity can pass through the sensor and signal to gas control valve that all is ok.
Failure of part, or FV event will 'short out' the sensor and shut off gas. Dirty environment will cause problems with all modern gas appliances. Replace the part and clean out water heater as described farther down on page.
Buy:
Flammable sensor kit
Rheem TRDRheem thermal device:

Buy:
Rheem TRD/ thermal device

Resource:
Verify activated TRD pdf
How to repair TRD
Raise water heater 18" off floor
Raise water heater 18" off floor to avoid flood damage and flammable vapors
Buy:
Water heater stand
4) Flammable vapor Lockout varies by brand, year and model.
When lighting water heater, if you have NO gas or pilot light but burner goes out when knob turned to ON ... then FV system is suspect.
Some water heaters have FV system that is tripped by variety of different problems including flammable vapors.
a) Push in TCO located on front of combustion chamber   See #3 above for TCO.
b) Keep air intake screen, or flame arrestor screen clean.  See #2 above. Dust and dirt can clog screen. Use feather duster, used compressed air. Install heater in clean environment free from dust and chemicals. Laundry room is not good location for FV water heater.
When arrestor screen is clogged, air flow slows down. Same amount of gas is being burned but heat is retained inside combustion chamber instead of venting up flue. The overheating trips FV system.
Solution for FV lockout event varies by brand and model, and by gas control valve. Try cleaning arrestor screen first. Push in TCO reset on front of combustion chamber.
Gas control valve may need to be replaced. FV sensor may need to be replaced. Part replacement depends on model and brand.
c) Keep combustion parts and chamber clean. Lazy yellow flame, instead of clear blue flame, and sooting on the burner surface indicate incomplete combustion. Explosive gas can accumulate. Can trip FVIR.
d) To prevent FV lockout and combustion problems: Perform maintenance shown in product manual, and keep air intake clean, allow plenty of fresh air, avoid dusty-dirty environments, and avoid flammable vapors.

Help prevent FVIR event by installing gas water heater at least 18" off the floor.
#1) Make sure there is adequate fresh air, and that air is clean and list free, and does not have trace chemicals.
#2) Always turn off gas to water heater when painting with oil-base paint or oil-base varnish etc, and when cleaning with solvent-based products, and when pouring gasoline etc.
For example when storing gasoline near water heater, the water heater should sit minimum 18" off floor, gasoline should be tightly capped, and do not pour gas to fill gas tank in same room as water heater or other gas appliance.
water heater stands Water heater should sit minimum 18" off floor
FV system is not 100% certain to protect from flammable vapor fire.
Gasoline vapors are heavier than air and generally do not rise above 18" in a typical ventilated room. Exceptions and dangers exist with all gas appliances and precautions should be taken.
Buy:
Water heater stand
FV lockout Rheem-Ruud-Richmond-GE
Air intake on side.
Some models use TRD glass vial trigger for overheating event. See image
Arrestor screen located under combustion burner.
Locate arrestor screen by removing burner
Clean arrestor screen with compressed air after removing burner. Look for broken glass.
Company might send glass vial replacement.
Reset TCO thermal reset on front of unit.
Rheem does not post service manuals
Buy:
Rheem water heaters at Amazon
FV sensor kit
Resources/ across all brands:
How to repair Rheem FVIR
FVIR intellivent troubleshoot .pdf
Bradford White service manual .pdf
Bradford White 2 .pdf
General FVIR troubleshoot .pdf
FV lockout AO Smith-American-State- Craftmaster-Reliance-Kenmore-Whirlpool
Air intake and arrestor screen are same and located under combustion burner on bottom of water heater. Best location for ez cleaning. See image No need to remove combustion parts to clean screen. Clean arrestor screen with feather duster/ compressed air.
Arrestor screen stops acceleration of flames into room.
Set 3-legged water heater on bricks for ez access to arrestor screen.
Reset TCO thermal reset on front of unit
Clean screen and reset TCO will usually restore FV lockout
AO Smith posts service manuals.
Service manuals also posted with gas control valves lower on this page
Buy:
AO Smith water heaters at Amazon
Reliance gas water heaters
50 gallon high efficiency
Bradford White-Boch-Lochinvar
Air intake on side. ScreenLok flame arrestor screen located inside. Image
Arrestor screen stops acceleration of flames into room.
Arrestor screen located under combustion burner.
Locate arrestor screen by removing burner.
If dust and dirt collects on arrestor screen over timer, clean with wire brush and compressed air after removing burner, and this will usually restore FV lockout.
TCO thermal reset on front of unit will cut off gas to pilot and gas control valve. Reset.
Bradford Posts service manuals.
Service manuals also posted here and also with gas control valves lower on this page
Buy:
Bradford White water heaters at Amazon
Bradford White water heater parts
FVIR Resources
How ScreenLok flame arrestor works
Bradford white FV troubleshoot
Bradford white power vent FV troubleshoot
Gas line connection
Buy:
Flexible gas line
Keep ends of pipe connections clean when installing or repairing gas supply or water heater. Do let stray pieces of teflon tape get inside pipe... wrap tape one second thread from end and not at end. Install sediment trap and loop on flexible gas line to keep out moisture and debris. Use black pipe and yellow flexible gas line.
Do not use galvanized pipe or flakes of galvanized will chip off and get into gas control. Do not use copper pipe unless approved locally..
Back to 10 things for troubleshooting water heater
5) Fuel supply
Natural gas and propane gas are different. Water heaters are purchased by type of gas used. Propane requires greater air supply ratio than natural gas. Propane has higher ignition temperature and burns hotter. The gas control valves are different with different threads for each type of gas. The burner and internal parts are different.
Natural gas is lighter than air and rises. Propane is heavier than air and falls to low spot. Do not install propane appliances below ground level where gas leak can accumulate in basement.
Water heaters are rated by BTU, or the amount of gas they burn. Gas lines and gas meters are rated by BTU for the amount of gas they can supply.  Higher elevations consume more gas to achieve same BTU output. New appliance, or too many appliances can affect amount of gas. If overall consumption of BTU is greater than supply, then water heater will not function. Larger gas meter, or gas line may be needed. Look at labels on each appliance. Call gas supplier.
Do not use copper pipe or galvanized pipe. Use only black pipe or yellow-colored flexible gas line. Check local codes for approved pipe that is non-reactive to the type of gas being used. Dirt, debris, moisture, galvanized flakes etc from wrong pipe or dirty pipes will get into the gas control valve and cause it to malfunction.
yellow is international color code for gas line. Acceptable to reuse flex line when installing new appliance.

Buy:
Flexible gas line
Approved PTFE tape
Gas grills
Resources:
LP heaters have left-hand threads
Convert water heater to different gas
Water heater conversion risk information
Cautions for convert to different gas
Image of cast iron burner for propane water heater
Safety
Water heater safety precautions before starting
Water heater precautions/ pdf
Gas-water-heater-Safety-Precautions
Gas valve safety
Thermal expansion
Insulation blanket

Resources:
Definitions and formulas/ pdf
Pipe size BTU chart
Pipe capacity
Square footage per BTU
Gas pipe capacity .pdf
gas line Use approved yellow gas line and flexible gas connections:

Buy:
Flexible gas line
pipe threading machine Pipe threading machine

Buy:
Pipe threading machine

Gas water heater ECO

Gas valves
Larger image
Gas valve manufacturers
Back to 10 things for troubleshooting water heater
6) Gas water heater thermostats are usually single-use after ECO trips.
Exception, some intellivent-style power-vent thermostats can be reset using button sequence.
-ECO Energy Cut Off is located inside the thermostat probe that extends into the tank to measure water temperature. When ECO senses overheating inside tank, the ECO trips and shuts off gas control.
-If ECO is tripped, or other malfunction, Gas valve must be replaced.
-ECO must have continuity so small current (derived from thermocouple or thermopile when heated by pilot light) can travel from thermostat through the ECO and back again to thermostat, completing the electric circuit, and signaling to gas control to function normally.
-If water heater burner or pilot light has gas, if pilot or burner flutters and goes out, then ECO is not tripped: Gas thermostat might still be bad, but FV system or related maintenance is first suspect.
-Do not install cold water line above gas valve where condensation drips on valve. 
Thermostat calibration means tank temperature matchs thermostat setting. All setting are approximate and vary widely. Adjust temperature, replace gas control if temperature setting is unreliable.
Resources
Pilot outage troubleshoot
Test ECO on Robertshaw- White Rodgers
ECO on Robershaw,White Rodgers, Honeywell pg 17
Read about resetting intellivent
How to adjust thermostat temperature
Buy
Gas water heater thermostats at Amazon
Back to 10 things for troubleshooting water heater
Icon gas valve
For atmospheric vent models
Range Low 55 - very hot 160
Average bath 110F
, typical water heater temp 120
ECO limit 199 F, ECO trips, gas valve fails
TP release water  at 170
All calibrations are approximate
Severe scalding risk over 135
Buy
Honeywell gas control at Amazon
American / Honeywell gas control at Amazon
Honeywell gas valve for propane
Honeywell natural gas valve
Reliance NG at Amazon
Reliance LP at Amazon
Kenmore water heater gas valve
Gas water heater timer fits this valve
Replacement instructions
How to test & replace Honeywell gas control valve
How to replace Honeywell gas control valve

Resources:
Adjust temp on Honeywell gas valve
Error codes
Error codes
To reset gas control, rotate dial to OFF, wait 10 minutes for gas to clear. Then relight.
State Error code/ troubleshoot/ service manual/ FVIR
Bradford White service manual
Error light blinking 4 times
How to light water heater
How to light water heater/ pdf
How to light Whirlpool energy smart

How to replace gas control valves
How to test gas control valve

How to install gas water heater

For power vent models
Range Low 90 - very hot 160
Average bath 110F, typical water heater temp 120
ECO limit 199 F, ECO trips, gas valve fails
Average bath 110F
ECO limit 199 F
TP release water  at 170
Buy
Example Honeywell gas control valve at Amazon
Reliance NG at Amazon
Replacement instructions
How to replace water heater gas valve

Resources:
Adjust temperature/ error codes on Honeywell
How to light Honeywell gas valve
Dampered Fury gas troubleshooting codes
Induced draft troubleshoot codes
Error codes
Error codes2
Error codes
Icon gas valve error codes
Service manual
Bradford White service manual 2
Test gas control/ from BW service manual
Sequence of operation
How to clean burner

Safety
Water heater safety precautions
Water heater precautions/ pdf
Gas-water-heater-Safety-Precautions
Gas valve safety
Thermal expansion
Insulation blanket

For power vent models
Range Low 80 to Hot 150
Error C flashes at 160
Buy
Buy Intellivent gas control at Amazon
White Rodgers/ Rheem Intellivent gas control
AO Smith intellivent
AO Smith Intellivent at Amazon
AO Smith White Rodgers at Amazon

Replacement instructions
How to replace water heater gas valve

Resources:
AO Smith Intellivent troubleshoot and FVIR test/ pdf
Error codes and adjust temp on Intelli-vent gas valve
How to light water heater
Troubleshoot Intellivent/ pdf
FVIR intellivent troubleshoot .pdf
Intellivent service manual
Intellivent FVIR troubleshoot and reset
Sample manual
Intellivent wiring
Power direct vent troubleshoot
Sequence of operation
Intellivent error codes-troubleshoot
Promax gas water heater manual
For resetting controller: After the unit has been off for at least a minute, plug it in, turn on the switch; within a few seconds, depress both arrow buttons on the controller, and hold them until the left light begins to blink.  Release them, and within a few seconds, push those arrow buttons in the following sequence:  L/R/L/L/R/L/R/R.  This should reset the controller.
White Rogers thermostat

Buy:
Camco White Rodgers at Amazon

Resources:
Troubleshooting/ pdf
How to light gas water heater
How to replace water heater gas valve


Remove gas valve
Buy:
Buy universal gas control wrench

gas valve setting
Larger image
Buy
Gas control valve thermostats at Amazon
Gas water heater thermostats at Amazon
Rheem gas control valve at Amazon
Gas control valve at Amazon
Camco White Rodgers at Amazon
Gas water heater timer fits this valve
Replacement instructions
How to replace water heater gas valve
Resources:
Service manual
Service manual 2
Service manual 3
Operation and safety
How to light water heater/pdf
General troubleshoot manual /pdf
White Rodgers gas control valve replacement pdf
Power vent water heater issues
Magnet testing
Test thermocouple
Gas valve testing
How to light gas water heater
White Rodgers NG replace, install, set temp
Honeywell Smart Valve AO Smith
Honeywell Smart Valve
Larger image

Resources:
Temperature settings and features
Smart valve error codes
Service manual
Install smart valve & troubleshoot
Robertshaw Natural gas control valve
Robertshaw Natural gas
Buy
Robert Shaw natural gas
RS Natural gas at Amazon
Camco RS at Amazon
Gas water heater timer fits this valve


Buy
Gas water heater thermostats at Amazon
Robert Shaw natural gas
Robert Shaw propane gas
Replacement instructions
How to replace water heater gas valve

Resources:
Robert Shaw models
Robert Shaw/ Unitrol troubleshooting/ pdf
General troubleshoot/ pdf
General troubleshoot manual /pdf
How to light water heater/pdf
Magnet testing
Test thermocouple
Gas valve testing
Operation and safety
Recalibrate gas control/ pdf
How to light gas water heater
Adjust pilot on unitrol gas control valve
How to test White Rodgers gas valve p14
How to test Honeywell Icon gas valve p23
How to test Robertshaw gas valve p14
Atwood gas control valve
Atwood gas control valve
Fits all Atwood water heater that have a pilot light

Buy
Atwood gas control valve at Amazon
Atwood parts at Amazon
Atwood water heaters and parts at Amazon
Resource:
How to replace gas control valve thermostat
Atwood water heater troubleshoot resources
Suburban water heater service manual

Honeywell L4006 water heater controller
Honeywell immersion thermostat
12-277 volt AC SPST controller
12-48 volt DC
Add to any hot water tank
Surface mount or immersion into tank
Temperature range: 100-180F
Water over 135 poses extreme danger of scalding.
Add mixing valve.

Buy 
Honeywell/ Rheem SP11798B
Honeywell L4006
Line Voltage Mechanical Thermostats

Resources:
Add another thermostat to gas or electric water heater
Advantages-disadvantages mixing valve
Control recirculation pump using controller
L4006 manual
L4006 wiring illustration
Honeywell L8104 water heater controller

SIT gas control valve for water heater
SIT gas control valve for water heater
How to light and set temperature SIT gas control


Kenmore with power anode rod
How to light Effex water heater
Effex service manual

Suburban water heater service manual

Whirlpool energy smart gas water heater manual

Robert shaw gas control valve
Robert Shaw 120Volt input gas control valve
Wiper Control and Gas Valve assembly
Triangle pointed upward is 120 degrees F
Replacement for Rheem power vent/
Buy

Rheem wiper SP20123A thermostat KIT
Wiper SP20123B valve/ no thermostat


Resources
Larger image
Error Codes and troubleshoot
Guardian power vent Robert Shaw error code
Rheem parts list
American power flex parts
General manual with lighting instructions
Replace water heater gas control and FV
Check pressure switch, blower, gas control
Sequence of operation
How to light water heater
To reset: turn the red control knob on and off 6 times within 30 seconds to reset the board.
bbbbbbbbbbbbbbbbbbb
Gas water heater burner
Larger image natural gas burner
Another images
NG gas burners are different than LP burners.
Connections to natural gas control valve are right handed.
Back to 10 things for troubleshooting water heater
7) Fuel supply to burner
The gas control valve lets gas flow into the combustion chamber through the pilot tube and manifold tube.
The pilot tube has an orifice that restricts gas flow for the type of gas and the amount of pilot flame needed.
The manifold tube is larger and sends gas to the burner in the amount to meet BTU rating of water heater.
The gas control valve must match the pilot and burner. 
Propane gas burner
Propane gas burner made of cast iron, shows manifold and pilot tubes, and thermocouple. Connections to gas control valve are left handed.
LP has more pressure and higher temp
ao smith burner assembly
Image shows natural gas burner assembly with piezo igniter, pilot tube, manifold tube, and thermocouple.
Some gas water heaters have modular burner assembly that is replaced whole, instead of individual parts.
Buy:
AO Smith burner assembly
Rheem burner assembly
Bradford White burner

Clean water heater burner line
Expanded image
Burners and burner assemblies can be cleaned serviced.
-Maintenance manuals suggest annually cleaning burner area with wire brush and vacuum cleaner.
Buy:
Tube cleaners at Amazon
Burner brush

Burner brush
Buy:
Tube cleaners at Amazon
Burner brush tube cleaner at Amazon
Burner Tube Brush Cleaners at Amazon
Appliance cleaning brushes at Amazon
Straw cleaning brush
Soot on gas burner
Soot implies unburned gas: dangerous situation
Gas may not be burning fully: lazy yellow flame indicates poor incoming air supply, dirty combustion parts, inadequate venting of combustion byproduct.


Soot on gas burner
Soot on top of heater implies danger of improper vent and backdraft #11 venting
Improper vent can blow out pilot light.

Flame should burn clear blue
Low gas pressure.
Dirty combustion parts.
Poor incoming air supply.
Inadequate venting.

This is dangerous because unburned gas can accumulate inside combustion chamber or inside the flue way. Causing ignition.
This situation will overheat combustion chamber and trip ECO, TCO and FV system, causing water heater to stop working.
Clean water heater burner
Use wire brush to clean burner assembly and combustion chamber. When re-starting cold tank, expect possible condensation dripping until tank reaches temperature.
This is the only time water should be apparent inside the combustion area of water heater, otherwise #11 bad vent or leaking water heater is suspect.
Cleaning water heater
Burner cleaning /pdf
Example: how to clean combustion chamber
Example: cleaning combustion chamber
Example: how to clean combustion chamber
Clean sediment out of water heater
Clean combustion chamber Effex water heater
Leaking water heater
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pilot light troubleshoot
Larger image
Back to 10 things for troubleshooting water heater
8) Thermocouple- thermopile, pilot light
Pilot light heats the thermocouple or thermopile, producing small millivoltage of electricity that travels to the gas control valve along the copper pilot tube. If the pilot light goes out, the lack of electric current shuts down the gas control valve and pilot light needs to be lit again. Older model gas water heaters required a long match and patience to relight pilot, while more recent water heaters are required to have sealed combustion chamber and use a piezo igniter to light pilot.
Thermocouple and thermopile are different. Thermopile is basically several thermocouples combined and produces more current than thermocouple. Thermocouples are used with older-style mechanical gas control valves that have a round dial on front. Thermopiles produce enough current to power small circuit board and are used with modern electronic gas control valves.

Look upward, and to one side, through sight glass to see that pilot flame is lit and clear blue color.
Causes for pilot outage:
Backdraft from shared vent and wind coming down the flue can blow out the pilot. see section 11 for venting. Dirty combustion parts and need for maintenance can also cause outage. see section 7. Bad thermopile or thermocouple. Misaligned thermocouple can also cause outage. Modern water heaters have solved the misalignment problem with fixed positioning and 1-piece replacement for combustion parts. see section 7. Bad gas control valve can cause pilot outage. see section 6.
Pilot light troubleshoot:
Clean the air intake, and get more fresh air to unit.
 Push in TCO located on front of combustion chamber.
Pilot troubleshoot resources
Test thermocouple
How to light gas water heater
Pilot light goes out
Burner goes out when control knob turned to ON
Pilot light will not stay lit/ pdf
Pilot outage/ pdf
Pilot problem or ECO or gas control?
Wind blows out pilot light
Pilot light or thermocouple?
Negative pressure blows out pilot
Pilot orifice
Pilot tube orifice
Clean with compressed air or carburetor cleaner
Do not rub with rag, or tube can clog
Pilot troubleshoot resources con't
Standing pilot light maintenance
Attic Ventilation and Pilot Outage
Pilot outage and negative pressure
Pilot light maintenance/ pdf
Ventilating tight-house/ pdf
Pilot light troubleshoot
pilot assembly
Buy:
Rheem Pilot assembly
AO Smith Pilot
Reliance Pilot
Kenmore Pilot
Bradford White Pilot
Gas water heater
Gas water heater
How to remove burner
Avoid Corrosive environments
Exposure to corrosive environments such as pool chemicals, process chemicals, bleach can damage burner parts.
Air is drawn into water heater, and if air contains trace amounts of chemical, or chemicals are burned in the flame, this will damage water heaters over time, and shorten life of water heater
Remove chemicals from same room as water heater.
-Chemicals that will corrode water heater parts and vent pipe include: 'Spray propellants, cleaning solvents, refrigerants, swimming pool chemicals, calcium and sodium chloride, household bleach, waxes and process chemicals ... all these chemicals are corrosive at very low levels with no odor."
Read Bradford White Pdf pg2-8   
Read Rheem pdf
Avoid corrosive atmospheres

piezo igniter
Buy:
AO Smith igniter
Rheem igniter
Reliance igniter
Piezo igniter
Today's water heaters have igniter to send spark to pilot light to start flame.
Older water heaters have open combustion chamber and pilot was lit with a match ... the piezo igniter helps prevent explosion into someone's face, or ignition of flammable vapors in the room caused by open flame.
The igniter is part of the FV flammable vapor prevention system where the combustion chamber is sealed so flames cannot easily travel from inside combustion chamber out into surrounding room.

How to test piezo igniter
How to check the igniter
Electronic spark troubleshoot
Troubleshoot hot surface ignition
Hot surface igniter troubleshoot
Power vent hot surface ignition

Buy:
Thermocouples at Amazon
Thermocouple adapters

Thermocouple Test and replacement
How to test water heater thermocouple
How to replace thermocouple pdf
How to replace thermocouple/ forum
Test thermocouple
Test thermocouple and thermopile




Thermocouple/ thermopile
Remove burner & replace thermocouple thermopile
Gas water heater burner assembly
How to Remove burner & replace thermocouple thermopile

How to light gas water heater
Pilot light goes out
Burner goes out when control knob turned to ON
Pilot light will not stay lit/ pdf
Pilot outage/ pdf
Attic Ventilation and Pilot Outage
Pilot outage and negative pressure
Pilot light maintenance/ pdf
Ventilating tight-house/ pdf
Pilot light troubleshoot
when thermostat set lower
Pilot problem or ECO or gas control?
Wind blows out pilot light
Pilot light or thermocouple?
Negative pressure blows out pilot

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Back to 10 things for troubleshooting water heater
9) Ignition of fuel supply
by pilot light or hot surface igniter ... issues: pilot light,
Hot surface igniter
Flame rod sensor
Location of flame sensor and igniter vary by model and brand of water heater.
Sand carbon deposits off igniter.
Avoid touching igniter
Larger image
Hot surface igniter troubleshoot
Hot surface ignition basics
Troubleshoot hot surface ignition
Hot surface igniter troubleshoot
Power vent hot surface ignition

Tip of flame sensor must be directly in front of burner port.
Use a nickel to set 7/64 gap.
Natural gas flame sensor will be bent, while propane will be straight.
Larger image
Intellivent troubleshoot Manual
Power vent surface ignition
Gas burner without piezo igniter
Larger image
Burner flame is yellow
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Power vent Back to 10 things for troubleshooting water heater
10) power vent water heaters
Power vent water heater can vent combustion gas through a sidewall vent.
How it works: "When the thermostat senses a need for hot water, a valve is opened which allows gas to flow to the closed solenoid valve. As gas pressure builds up within the solenoid,  the gas pressure switch closes and 24 VAC flows to the blower relay.  The  blower  relay  contacts  close and  send  115  VAC  to  the  vent  blower  which  turns  it  on.  Air  flow  from  the vent  blower  closes  the  air  pressure  switch    sending  24  VAC  to  the  solenoid  valve.  The  solenoid  valve  opens  and allows gas to flow to the burner which is lit by the pilot or igniter"
Blower: less than 5 amps consumption @ 120 volt. 120 volt x 5 amp = 600 watts running with 1200 watts start-up.

Resources:
Power vents:
Power vent water heater issues
Anode covered by power vent

water heater blower motor  Blower
Power vent water heaters use a blower to vent gas by-product from water heater. Blower requires 120 volt grounded outlet. Electric outlet for power vent and flue damper water heaters should be dedicated, and surge protected. Do not use extension cord for power vent and flue-dampered water heaters.
Blower is connected to gas control valve with a wire, called the control cable. The gas control uses a firing sequence to activate the blower and start moving air upwards just before the burner fires up.
Blower, control cable, gas control valve, and pressure switch are part of troubleshooting. Eliminate the obvious: Check the blower first, and gas control valve last.

Buy blower:
Water heater blowers at Amazon

Blower troubleshoot
Test pressure switch
Power vent troubleshoot
Troubleshoot hot surface ignition
How to check blower motor
Check blower motor
water heater blowers Blowers: Fasco, AO Smith, Bradford White, Rheem power vent water heater exhaust draft-induced blowers
Buy blower
:
Water heater blowers at Amazon
Other types blowers
Fasco multi-purpose blowers
AO Smith multi-purpose motors and blowers
Furnace blowers
water heater pressure switch Pressure switch or vacuum switch
Generally, to check if blower is good and pressure switch is bad, you bypass the pressure switch and connect blower directly to 120 volt outlet, running a pigtail to the blower or plugging blower directly into outlet.
Pressure switch troubleshoot
Test pressure switch
Air pressure switch testing
Intellivent wiring
Pressure switch replacement
Bradford White pressure switch replacement
Check pressure switch
water heater pressure switch Pressure switch/ Vacuum switch for water heaters
There are 3 major water heater manufacturers, AO Smith, Bradford White, Rheem, that make all the other brands from Kenmore, Craftmaster, Whirlpool, American, Reliant (AO Smith) to Reliance (Rheem)
Buy water heater pressure switch:
Rheem water heater pressure switch
Bradford White pressure switch
AO Smith pressure switch
Outlet polarity Polarity
If gas valve is connected to electricity, the outlet polarity must be correct
Water heater must be grounded. Poor ground can prevent flame. GFCI circuit can cause short cycling. If outlet is not dedicated or has GFCI, other loads such as florescent lighting can cause short cycling.

Unplug cord. Test for continuity between ground prong on plug and manifold tube on gas valve.
Connect water heater to different outlet. Test outlet with circuit analyzer
Minimum distance of vent pipe from window   
Larger image with more information
Minimum distance of vent pipe from window
Side-wall vent pipe must be 4 feet away from windows and doors. And 3 feet away from inside corners.
Power direct-vent clearances
Venting a gas water heater
Conditions where outdoor air supply is needed
Power vent
Venting power vent models
Read product manual for venting specifications
Example power vent manual p17
Minimum vent distance from window
Power vent tables
Power vent troubleshoot
Typical power vent manual
Typical power vent manual2
Typical service manual
Gas venting specs
Conditions where outdoor air supply is needed
General troubleshoot and service manuals:
Troubleshoot gas water heater
Troubleshoot gas water heater2
Test if thermal device needs replacement/ pdf
Reliance 2006 troubleshoot handbook/ pdf
AO-Smith-service-manual/ pdf
AO Smith service manual
AO Smith service manuals
AO Smith 2006 service handbook
AO Smith Technical bulletins
Bradford White Service Manual/ pdf
Bradford White technical bulletins
American troubleshooting guides
State service manual
Icon gas valve error codes
Dampered water heater troubleshoot/ pdf
Hot surface igniter troubleshoot/ pdf
American gas water heater service manual
Intellivent service manual
Whirlpool Energy Smart Gas Service/ pdf
Polaris troubleshoot and install manual
Rheem service bulletin
Rheem-Ruud 2011 parts list/ pdf
Rheem parts 2010
Rheem-Ruud 2009 parts by model number
Rheem 2009 parts list
General how-to
Find age of water heater
How to replace drain valve
Leaking water heater
How to read the gas meter
Clean sediment out of tank and periodic flushing
How to install electric water heater
Thermal expansion tank
Noisy-gas-water-heater

Typical manuals
Typical power vent manual
Sample Rheem Gas water heater manual
AO smith Service manuals
flue pipe



Use 3-4" galvanized, stainless or PVC pipe.
Water heater manual will specify vent.
Side wall terminations are for power vent models.
Do not use aluminum or other low-temperature material
Assemble lower sections so they fit inside the next higher section to ensure no leakage.
Attach vent pipe sections with 3 screws.
Add vent tape to ensure no leakage.

Back to 10 things for troubleshooting water heater
11) Venting combustion byproduct
Do not use aluminum vent pipe. Use 3"-4"  steel galvanized, stainless or PVC pipe.
During water heater combustion, hydrogen content of fuel is burned, resulting in hot gases that travel upward and out the vent pipe. Obstructed vent will slow or halt combustion, resulting in tripped ECO, yellow flame instead of blue. Adequate venting or air draw up vent is required so gases vent outside.
Atmospheric vent has no blower or mechanism to assist upward flow of vent gasses. The venting action is a natural upward flow of hot air, plus the natural upward convection of air.
Power vent and flue-damper water heaters push vent by-product up the vent pipe. If blower or pressure switch or firing sequence is not functioning, the vent gasses do not travel up vent pipe.
Negative air pressure
Wind
Rusted flue pipe -or water dripping down from flue pipe:
1. Vent cover could be missing > rain water entering flue (replace cover)
2. Flue pipe clogged with bird nest or come apart or damp from improper venting: danger of odorless Carbon Monoxide poisoning

Buy:

Carbon monoxide detector
Vent tape
Water heater vent hood

Simple test for proper venting: Check that pipes are not rusted or covered with white condensate. There is no water on top of tank. Burner inspection does not show excessive rusting. Steps: Turn off water heater and wait 1-2 hours for heat to stop rising from tank. Hold lit match within 1" of vent hood and see if smoke is drawn into vent. If smoke does not draw, then check for vent obstruction on roof, or call plumber.
Resources:
See image of test
Vent draft test
Gas venting specs
Square footage per BTU
Ventilating tight-house/ pdf
Pilot outage and negative pressure
Soot on gas burner
Soot on top of heater also implies danger of improper vent and backdraft.
Improper location of vent on roof, and incorrect clearances, or windy location can stop vent gas from leaving vent pipe. If vent gas cannot escape at top of pipe, it can be entering house at the vent hood. Soot on top of heater is evidence. If pilot goes out, the improper draft can be blowing out pilot light.
Soot on top of heater can be caused by backdraft where vent gasses are being blown back onto water heater because of shared vent pipe with furnace or other gas appliance. Read next section.
Backdraft Is your furnace causing water heater to malfunction? Furnace, kitchen-bath bent fans etc can affect vent draft on water heater. Called negative pressure.
Is there evidence of rusting etc on top of heater, next to the draft hood? Is the furnace room particularly cold or wet? This is evidence of backdraft.
Here is a simple, but telling test. When the water heater first fires up, a little heat will spill from the draft hood. It should only spill for a second or two under normal circumstances. So, with the furnace off, turn the temperature on your heater up to cause it to fire up (you might make a mark on the thermostat dial so it can be put back to the same place). Quickly, put the back of your hand to the draft hood to feel any heat spilling out. Count the seconds. Return the heater to normal. Now wait a bit and fire up the furnace. Feel for any spillage at the water heater draft hood with the water heater off. Count seconds. Now fire up the water heater (furnace running) and check for spillage again.
If furnace and water heater both vent into same chimney, the draft might not work properly. Water heater should have dedicated vent. For example the chimney vent pipe is is eight inch, but the two vents (from furnace and water heater) going to it are both four inch. That bigger vent might be oversized and hard to warm properly for good drafting.
If the furnace is power vent, and fan or vent will overpower natural draft. Having the furnace and water heater vents combined will cause problems. Likely the
right fix is to run two, separate three inch vents.
Water on top of heater. Rusted vent pipe. White condensate on pipes.
Inadequate draft, or improperly installed vent pipe can cause condensation inside pipe that will rust and cause white condensate.
Missing roof cap will cause water on top of heater that will rust out the water heater.

Never install more than 1 elbow on sidewall vents
Straight shot is always best shot. Elbows slow venting and cause backdraft.
Resources:
Gas venting specs
Direct vent clearances
Conditions where outdoor vent is required
 
Vent Gas Odor
Lack of air supply
  -Clean air intake screen, open window
  Ventilating tight-house/ pdf
Improper vent
  -Read product manual for vent requirement
Downdraft
Poor combustion
  -Clean combustion parts, service unit
CO poisoning
If joints fall apart, or vent is improperly installed, hot gases enter home posing risk of odorless CO poisoning. Symptoms: headache that goes away when outside in fresh air. Unconsciousness.
Remove affected people from home and lay on sides, not on back. Call emergency help.
call plumber. Attach vent pipe sections with 3 screws and then cover joints with aluminum tape.
Buy:

Vent tape
Carbon monoxide detector
Corrosion of parts.
Chemicals can damage burner parts
Do not expose water heater to stored chemicals, swimming pool chemicals, laundry equipment
Remove chemicals from same room as water heater.
-Chemicals corrode water heater parts and vent pipe. 'Spray propellants, cleaning solvents, refrigerants, swimming pool chemicals, calcium and sodium chloride, household bleach, waxes and process chemicals are corrosive at very low levels with no odor."
Poor venting can damage parts
When there is inadequate draw, the water vapor cools and condenses on inside wall of vent pipe. This condensation water is acidic (pH 3-5) and corrosive. It will corrode steel metals and other materials.
Improper venting causes water to drip down vent into combustion chamber of gas water heater. Parts inside combustion chamber rust. Holes develop in bottom of water heater. Inspect combustion chamber for rust and water.
Avoid corrosive atmospheres
Hybrid:
Heat pump water heaters at Amazon
GE 50 gallon hybrid heat pump at Amazon
Reliance 80 gallon heat pump at Amazon
Air tap: add to existing electric water heater at Amazon
Buy:
Tent City USA tankless water heater/ off grid
Additional links
Gas and electric water heaters Support the economy:
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50 gallon Gas water heaters at Amazon
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40 gallon electric water heaters at Amazon
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How to install electric water heater
Troubleshoot gas water heater
Troubleshoot electric water heater
Point of use water heaters
Resources:
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Icon gas valve

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How to wire tankless electric


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Titan tankless
Anode rods anode rods
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Point of use water heater
Type 1 and type 2 surge protection surge protection

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