I'm not a plumber but I swear and cuss like a Surveyor when I try to be one at home.
Here is my story:
Yesterday was my first day off in two weeks. I slept in to 5:30am, get up find note from wife, no hot water, oh boy time for fun. Luckily master bath has it's own WH. I take a hot shower then figure out why main WH isn't running. I watch some YouTube videos, it seems easy to replace the thermocouple. I get the burner assembly out, but it doesn't look simple. Find the manual (also found my circuit breaker list that has been missing for two years), it says replace the whole pilot assembly which is $77 for the part not 10 bucks for a hardware store thermocouple. Damn. Can't get one on Saturday but can order it. Somewhere on the internet it says to blow out the pilot tube, I apply compressed air, some crud comes out, then reinstall the burner assembly to see if I fixed it. I can't get the pilot to light even allowing time for gas to come through. Go to order part, all ready to put in info and CC, figure I will try one more time. I remove the burner assembly again and blow more air then this time I verify it is coming out pilot end. I reinstall the burner 2nd time then allow two minutes to bleed air out, click click click, pilot lights, hold button for one minute, turn knob and WOOSH main burner comes on and stays on. It took a long time to cycle off because it started out with 50 gallons of luke warm water in there, look in the stupid little window and there is a good looking pilot flame in there. Run the hot water for a while and WOOSH main burner comes on again which is a big relief.
Remember, "If I was going to build a wall, I would ask to know what I was walling in and walling out." -Robert Frost.