This product can be used on natural gas lines, but yellow PTFE tape is recommended as it’s a visual sign to inspectors that it meets code. White PTFE is single density, while yellow PTFE is double density, so it’s heavier and requires less wraps than the white. Yellow is a requirement in some areas, so best to just go with it to be safe—Oatey makes yellow PTFE tape as well.
I have used it for high pressure air lines and it seals tight, so I know it will work, but there is a version of this that is specific for gas lines. It is colored yellow.
Yes this tape can be used in this application.
FASTape is HomeDepot's brand name for Hercules-Megatape from Oatey. The specifications for Megatape can be found in the Submittal pdf file on Oatey website.
This tape is compatible with OVC and metal pipes.
The main difference on the tapes are a variance in density and color. Yellow is the universal color for gas and would tell anyone working around those joints that natural gas runs through the lines. Tape can be used in most applications and will work in yours.
If you have more dry tape use that. Also, it provides an excellent seal so maybe the leak is caused by something else, such as the tread on the "small pipe". Lastly, you may want to snug down the nut on the pipe.
FASTape is HomeDepot's brand name for Hercules-Megatape from Oatey. You can find the specifications for Megatape on Oatey website.