50 gallon NG Water heater still in warranty, but for parts only. Burner and pilot would light but go out later. Whirlpool sent me the complete pilot/thermocouple assembly - no help (I used to be able to get the burner to light, but not now). Then they sent me a new gas valve. All installed. Pilot will light but goes out as soon as I release the Pilot "button". Since I have essentially replaced everything there is, what can the problem be ? Only thing I can come up with is the pilot is not hitting the new thermocouple, but it is very hard to see. Plus everything is locked down and not like the old ones where you could adjust things.

The only thing that I can suggest is from the Expert, Speedball1 (Tom) as he says

Look out next to the gas meter. Is there a tee with a capped pipe sticking down out of it? If so that's a drip loop. This picks up any moisture in the gas line and stores it in the capped pipe before it gets to the heater. Sometimes the capped pipe gets full allowing water to enter the gas line and extinguish the pilot light. Turn the gas off at the meter stop, remove the hard cap and drain the capped line. After you tape the threads and replace the cap turn the gas on and test the joint by painting it with dish detergent. Any bubbles, shut the gas off and re do the joint, I hope it will work

John

Agree w/ afaroo. There might also be a drip leg right at the WH itself. Same problem, same cure.

Seems all of my reply did not make it, so trying this route. Drip leg was clear. Had to be removed and re-installed to add the new controls. Water ran down and into pilot area when draining. Was clear (but still moist) when re-lighting it. Is there any way to increase the size of the pilot flame ? I'm thinking if we could increase slightly, it might hit the thermocouple better. Since the pilot assembly and controls are all new, the anti-flashback screen had to be clear, and I don't see anything left.

Hi Jim...

This is a closed combustion chamber water heater... yes? If so, remove the screws/nuts on the combustion chamber so the chamber remains open to the air a bit and then try lighting the pilot and see if it stays lit. If it does and the water heater fires when the gas valve is turned ON then most likely the air filter/combustion air screen to the heater is clogged and will need to be unclogged.

Try opening the combustion chamber... let me know what happens... OK?

Mark