On Wednesday, August 15, 2018 at 2:44:23 AM UTC-4, Vic Smith wrote:
On Tue, 14 Aug 2018 19:51:10 -0400, Wade Garrett wrote:

Seems to me though if you blow the air out of the line through the
loosened connection then turn the gas off prior to re-tightening the
connection, air will get back in the line. No?

No. Like "bleeding" anything else, you're dealing with a positive pressure against
atmospheric pressure. The atmospheric can't overcome the positive.
But I've never had to "bleed" air out of natural gas lines. The appliance does that.
A 20 year old dryer probably has a pilot light. That's connected at the gas valve, so
lighting the pilot serves to bleed out the gas line when it's been disconnected.

Except that you can't light the pilot light until the air comes out of
the line first. If it's 50 ft of 1" pipe that was worked on,
that could take awhile and
if you're a plumber, the customer isn't going to like you sitting there
with your butt crack showing for hours, running up the bill. For a homeowner,
I guess if you want to wait and monitor it, the gas will eventually get
there.