"Scott Lurndal" wrote in message
. ..


Found this on-line:

TEFLON TAPE:

When PTFE (Teflon) tape first became available they only made it in the
common single density type, which we commonly find in the hardware and
home
supply stores. Later they began making a double density version, which was
twice
as thick. Many state and local codes then adopted the double density type
as
mandatory when making connections for natural gas however since both
products
were the same color (white) it was difficult for inspectors to be sure
which
product had been used. PTFE tape is now made in numerous varieties and
they have
issued a color standard to determine which type should be used.

WHITE-Single density- should only be used on NPT threads up to 3/8 inch.

Actually I have found the White in at least 2 densitys. I have seen some
that is so thin that it is difficult to work with, like plastic wrap used
for food storage. I now buy Yellow so that I do not have to wonder if I am
getting the thicker easier to manage White tape or the very thin stuff. The
thin Teflon tape is usually packaged with products like new water faucets.


YELLOW- Double Density- yellow double density is often labeled as "Gas
type"
RED-Triple Density: (Note-the container is red but the tape itself appears
as a pale pink color). Presently required on all joints ½" diameter or
greater.
GREEN- Oil Free PTFE tape- Required for use on all lines conveying oxygen
(I.E. medical oxygen or welding oxygen lines).
COPPER COLOR- contains granules of copper and is to be used as a thread
lubricant but is
not approved as a thread sealant. (Generally it is used as a thread
lubricant on bolts
or pipe threads for mechanical applications where no physical seal is
required.)

PTFE tape is only approved as a thread seal when applied correctly. To
apply you begin at
the end of the pipe and wrap the tape under tension in the direction of
the thread turns.
Each successive layer should overlap the previous layer by ½ to 2/3 and
continue wrapping
until the entire threaded portion of the pipe is covered. (Minimum of 3
full turns).