I have a branch of gas service run from main gas pipe to my greenhouse in order to use gas heater during the winter. Coming from the ground I join plastic with black pipe going inside of green house. Do I have to put any special union part in between? Thanks

What kind of "plastic" gas pipe do you plan on using ? Please, verify before you proceed. Back to you. Milo

Is it yellow plastic underground? Can you post a pic or two of the setup?