Pilot won't light on Rheem Fury G 29-30

Usually if they won't re-light it's a problem with the orifice on the pilot itself. The thermocouple won't cause it to re-light but it will prevent it from staying on after being lit. Just make sure you have valve set to pilot when you press the red button down to light. You can take out the burner by removing the gas and thermocouple lines, unscrew the orifice and use like a wire brush bristle to clean out the hole in the orifice.

Tripped FV or TRD, or bad gas control valve, low gas pressure, air in gas line.
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
http://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html#intellivent
Unfortunately, Rheem does not post service manuals. Other companies post service manual, but only Rheem uses TRD FV system, while other companies use arrestor screen.
http://waterheatertimer.org/How-to-repair-Rheem-TRD.html
Add a comment and say what you discover.

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Open a nearby window to let in plenty of air and see if problem continues.
Problem might be something simple like vent backflow blowing out pilot, or more complicated like bad gas control, or combination of problems listed below.
Suspects include:
Faulty gas control thermostat.
Air in gas line.
Low gas pressure.
Hot attic air.
Insufficient air, or dirty air intake.
Dirty combustion parts, and tubes.
Thermocouple not sitting in flame.
Thermocouple tightened too much. Finger tight + 1/4 turn. No joint compound or teflon tape.
Bad venting.
Backflow of air down vent pipe caused by tight house and/or other vent fans in house.

Open following link for resources, illustrations and reading:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#clean
http://waterheatertimer.org/pdf/Bosch_Checking_the_draft.pdf
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf

If pilot lights and flame is robust and clear blue, and pilot goes out later, then some suspects can be excluded: air in gas line, low gas pressure, thermocouple is overtightened (finger-tight + 1/4 turn), thermocouple not positioned correctly in the flame, dirty pilot tube.
If flame is yellowish and small: then clean pilot tube and combustion parts.
http://waterheatertimer.org/How-to-install-gas-water-heater.html#clean
Remaining suspects can include: air in gas line, low gas pressure, bad gas control valve, tight house so household vent fans pull air down water heater vent that blows out pilot, hot attic with inadequate ventilation, water dripping down vent.

Open following links to read troubleshoot resources.
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot

hi there
sounds like a thermo coupling or faulty gas valve.possible circuit board fault.

hope this steers you in the right direction

The question is? I'll assume you cylinder is the water heater, right?
On the heater (water) you will find or see the red controls and a sheet metal cover over a hole. Remove the cover and this is where you light the pilot light. Press down on the red dial and turn it to pilot. In that position you will be able to press the red button . Geyt a long match or bbq lighter, then, holding down the red button dow for a minute or so and place a match or lighter into yhe area where the lines go The flame will catch the gas and lite the pilot if yo simply move your glame around. When the flame catch on the pilot, continue holding the button down for sveral minutes until the buld the flame isheating gets hot. Then release the buton and turn the main dial to on. The main burner should fire up. If not, and the pilot goes out, repeat the process. The bulb in the pilot flame is a thermocoupler that shuts all gas off if it doesn't detect a pilot flame, so hold the button down longer. If the pilot goes out when you release the button, The thermocoupler is no good and needs replacing. Good Luck_Ned_

The thermocouple is a screw in type or 2 wire. You can check the dc MILI volt output with a multimeter. It should probably make 500-750miliVDC when heated. Be sure no plastic from the thermocouple wrapper was on the threads, will not work like that. To light did you push and hold the valve for 30 sec after lighting the pilot then turn to run after the pilot was burning? There is a slight chance the gas valve is bad but not likely. Check the wireing on the thermocouple to the gas valve.

Hi I would try changing the thermocouple

Sometimes it is necessary to turn the temperature dial all the way back to the coldest setting with the gas valve in the off position in order to reset the safety on some gas water heaters. Give it a try

Air in system. Make sure there is no sources of ignition and loosen the supply line at the heater and purge all air. Mske sure your source valve is open. then turn off yje heater after tightening the line. Let sit in off position for 15 minutes. Then turn therm knob to on slowly and then over to pilot, depress pilot button and hold a ffew seconds. Pilot should light. If so, hold for a few and then release and turn ti on position. Good Luck.