Interesting. But the red-handled valve was completely removed from the outdoor assembly to there would presumably have been an open pipe after the yellow valve. Open atmosphere.

There is always the chance that yellow valve does not go to the grill. The tap test might confirm but it takes two people.

For what it's worth. I did have a regulator go bad on my natural gas grill. Similar set up on a out door grill. Changed the regulator and gas was flowing again.

quote:

Originally posted by Aeteocles:
So we've got gas just before the pipe goes underground.

Did you happen to operate the yellow valve and witness the hiss stop? Wackier piping has happened. That could be an inlet, feeding the WH and grill from the other direction (although it would make no sense to have a union *before* the gas valve).

Yes, the yellow valve is operable and the hiss stops with valve operation. I actually turned the valve off before cracking the union open, as I didn't want an uncontrollable flow of gas coming at me in case I broke the pipe trying to loosen it.

Valve off, cracked the big nut open a few turns, valve on, check for hiss and gas, operate valve on and off, valve on again, turn nut close, check for no hiss and no gas smell, valve off.