Problem is not thermocouple:
Thermocouple should be finger-tight plus 1/4 turn
Overtightening will short thermocouple against gas control valve, and solenoid switch will not open, and no gas will reach pilot once red button is released.
Tip of thermocouple has to sit in the pilot flame.
If pilot flame will stay on, then thermocouple is good.
Problem is not solenoid switch.
The gas control valve solenoid opens and closes gas supply to gas control valve.
On mechanical gas control valve, when you push down the red button to light pilot, then you are opening the solenoid and letting gas flow into gas control valve.
When heat is applied to thermocouple, a small electric current travels to gas control valve, and this causes solenoid to stay open.
If you extinguish pilot, then no current travels to gas control, and solenoid clicks off.
You can hear it click, and this is how you test it.
However, since you are getting gas to pilot light, then the solenoid is not the problem.
This leaves 4 possible problems:
1) Bad gas control valve thermostat.http://waterheatertimer.org/pdf/How-to-replace-water-heater-gas-valve.pdf
2) Inadequate gas pressure. Call gas company.
3) Dirty combustion parts. Clean the burner with wire brush and water.
4) Clogged air intake on FV water heaters: Rheem FV gas water heaters have glass vial that will break if combustion is slowed by clogged air intake.http://waterheatertimer.org/How-to-repair-Rheem-TRD.htmlhttp://waterheatertimer.org/How-to-troubleshoot-gas-water-heater.html
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