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How to replace thermostat on gas water heater
Gas water heater thermostats at Amazon
Icon gas valve This Honeywell gas thermostat is NOT removed from tank ... instructions on separate page
All other thermostats are removed from tank and covered on this page
Resource  for replacing atmospheric Honeywell:
How to replace atmospheric Honeywell gas water heater thermostat
This Honeywell gas water heater thermostat IS removed from tank and is covered on this page:
Range 90, Hot is 120 F // Very Hot 156, ECO limit 199 F
Resource .pdf:
How to replace power vent water heater gas valve 1
How to replace power vent gas control thermostat 2
Also read instructions below on this page
How to light water heater / pdf
Bradford White power vent service manual/ pdf
Error codes and service manuals
Example Honeywell gas control valve at Amazon
Intellivent gas water heater thermostat IS removed from tank
Intellivent gas water heater thermostat can be RESET
Read about resetting intellivent
How to light water heater
Intellivent error codes and service manuals
Also read instructions below on this page

Buy Intellivent gas control at Amazon
White Rodgers/ Rheem Intellivent gas control
AO Smith intellivent
Thermostat is located inside copper tube
To replace thermostat, gas control valve must be replaced
Service manuals for all types gas control valves


Gas water heater thermostats at Amazon
Thermostats are usually single-use after ECO trips
Water heater Gas thermostat has Energy Cut Off
Gas water heater ECOWhen ECO senses overheating inside tank, the ECO trips and shuts off gas.
If water heater burner or pilot has gas, then ECO is not tripped.
Gas valve must be replaced (except Intellivent which can be reset).
ECO must have continuity
Read more
Test ECO on Robertshaw- White Rodgers
Read about resetting intellivent
Gas water heater thermostats at Amazon
Replacement starts here for all models
Following steps apply to all gas water heater thermostats
Natural gas and Propane
Except Honeywell shown at top of page
Service manuals
White rodgers gas control thermostat
Before spending money on repairs, check anode rod
Anode will stop tank from rusting.
If anode rod is depleted, then install new anode to prevent steel tank from rusting.
Anode is located on top of tank, either regular 1-1/16” hex head located on top of heater in separate anode port, or combo anode that is connected to hot water nipple. Or both is water heater has 2 anodes.
Read more about replacing anode rod
Leaking water heater
Anode rods at Amazon
1-1/16" impact socket at Amazon
Breaker bar at Amazon
Adapter from 3/8: socket to 1/2" socket
gas control label Identify and order new gas thermostat using label on side
Order new gas control valve thermostat online
If gas control is discontinued, there are usually replacements available.

Do not re-use old thermostats
Do not install different model on water heater
Do not mix propane or natural gas
Do not convert water heater to different gas.
Propane burns hotter and requires cast iron burner, and propane gas has more pressure> absolute danger to convert to different gas
Gas water heater thermostats at Amazon
Turn off gas to water heater
Locate gas shut off. Handle will be parallel with gas line when gas is ON Rotate gas shut off handle perpendicular across line to shut gas OFF.

Let water heater cool for a couple hours.
Gas water heater thermostat
Larger image
Connections on bottom of gas control
Note tubes connected on bottom of gas control.
For propane, threads are reverse. Natural gas, threads are regular.
Note how tight each is when removing, so re-installation is about same.
These connections do not need pipe sealant or teflon tape.
Remove gas line from side of gas control
Keep gas connections clean/ avoid debris inside gas valve
Gas line is re-used.
Use only black pipe or flexible yellow gas line.
Make sure gas line stays clean, so dirt will not enter new gas control.
Gas line connection
Black pipe union
Black pipe union
Keep pipe clean
Protect end of pipe from dirt
Remove old teflon tape.
Keep all debris from inside of pipe.
Yellow flexible gas line
Flexible gas lines at Amazon
Remove gas thermostat Use 1/2" galvanized pipe as handle
Screw piece of galvanized pipe into gas control valve and use as handle to unscrew old gas control.
Loosen gas control using weight of water inside tank, then drain tank before removing completely.
Use weight of water in tank to loosen gas valve
... then Drain tank
Turn off water and drain tank completely
If tank won't drain, connect washing machine hose and water hose to drain valve to flush open.
Install new thermostat
New gas control should have sealant on threads. If not, add 6 wraps white teflon tape to threads.
Install new gas control into tank. Must be tight so pressurized hot water doesn’t leak from tank.

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Re-attach tubes under gas control
Do not overtighten.
No teflon tape on tubes under gas control.
Thermocouple is finger-tight plus ”
Electronic gas controls have wires for thermopile and do not have thermocouple.
Gas line connection Re-attach gas line 
Using yellow teflon tape, or gas-approved thread sealant
Yellow is for gas.
Do not let pieces Teflon, or pipe sealant, into gas line where it can enter gas control.
Do not overtighten gas line where it connects to gas control to avoid damage to new control.
Gas has less pressure than water line.
Test for gas leak
Larger image

Gas pressure is low, so it takes time before leak will show.
Use soapy water to check for leaks on gas line, and on tubes under new gas control.
Test for gas leak
a) Test pipes: Mix liquid soap with water and use brush to put around around gas line joints to see if there are bubbles. Use plenty of soapy water. May take some time for bubbles to appear since gas is under low pressure.
Soap bubbles coming from joint indicate leak: retighten pipes, use teflon tape on yellow flex pipe and black pipe.
Do not overtighten pipes or damage can occur to gas control valve.

b) Test factory-installed connections located below gas control valve
Manifold and pilot tube connections located under the gas control valve do NOT use teflon tape.
See image of manifold and pilot tubes
If either tube under gas control valve is leaking, just tighten a little bit. Do not overtighten.
Manifold and pilot tube: look for reverse thread on LP water heater. Regular thread on NG water heater
Remember: Natural gas and propane gas both have less pressure on the line than water pipes, so gas pipes are easy to seal with ordinary wrench. If you can install water line without leaking, you can do the same with gas line. Do not over-tighten connections.
Gas odor will be present if gas line has leak. Smell close to floor since some gas can be heavier than air and will settle downward. If gas is present, leave house immediately and call gas company. Turn off main shut-off at gas meter.

Bathtub running full stream before lighting water heater
Tank must be full of water before lighting
18) Fill tank completely with water until water is coming out of tub spout.
Open tub spout on hot side and wait for full stream of water.
Next open TP valve for a moment to bleed last of air from tank.
Turn off tub spout and light heater.
Tank cannot have any air when burner is turned on or damage can occur to tank.

How to light typical gas water heater
Read directions printed on side of your tank
Light new water heater as shown on label located front of water heater
Read product manual for tips and advisories.
How to light gas water heater by type of gas control valve
Note: New gas heater might have small water leak when first fired up because of condensation
Ignore a bit of water inside combustion area or bottom of tank.
This water is condensation and will disappear as tank reaches set temperature.
Any cold tank can show same condensation when fired up.
Water pipes should not be leaking.
Water should not be dripping down vent pipe: this signals bad venting or other vent problem.
Don't worry excessively, but if needed, post questions on professional water heater forum: The Tank
16 things needed for gas water heater & .pdf resources

Gas water heater burner assembly
What you need for operation of gas water heater.
General troubleshoot
1) Basic parts and operation
2) Adequate incoming air supply ... issues: closed doors, tightly insulated house, very hot attic.
3) Adequate air supply getting to burner... issues: dirty vent screen, dirty environment, maintenance.
4) Thermal cutoff  ... TCO ... issues: failed part, maintenance, vent.

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

8) Fuel supply from thermostat to burner ... issues: maintenance, thermocouple-thermopile, gas control valve.
9) Clean and replace burner ... issue: periodic maintenance requires burner inspection, cleaning, and possible replacement

10) Functioning thermopile-thermocouple-pilot light ... issues: misalignment, failure of part.
11) Ignition of fuel supply by pilot light or hot surface igniter ... issues: pilot light, piezo igniter, electrode.

12) Power vent water heater troubleshoot ... issues: pressure switch, blower, blower sequence from gas control, outlet polarity
13) Venting combustion byproduct .... issues: vent in disrepair, other vents in house drawing air

14) Misc troubleshoot manuals
15) How to install gas water heater
16) How to maintain water heater
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