"John B" wrote in message
...
I paid a high price for the yellow stuff, for fixing gas lines. This tape
is thicker than the white I use for water plumbing.

I have not "googled" this or done any other search. I am thinking that
gas
plumbing, being subjected to lower pressure than water plumbing, is not
tightened as much. Hence the thicker tape. Conversely, one would not
want
thick tape on threads that must be tightened strongly.

Gas attacks teflon tape, or at least an additive does. The yellow tape is
denser and resists the attack.

I have used yellow on water without any problems, just because it happened
to be what I found first.