text: why ream gas pipe? won't gas find it's way through even in the dark? there are a few reasons... to keep the correct volume of gas flowing to keep small peices of metal  from flowing with the gas and causing small clogs. so you dont cut your fingers and hands and most importantly, to make sure when you tighten up a fitting such as a union, or a coupling that you have a good seal (even though you use dope) so you dont have any leaks when you do a pressure test.