I have a 40,000 BTU Heat-N-Glow fireplace insert that is currently connected to my natural gas via a 1/2 inch copper line. Even though the unit came with an adjustable flame height control I right now only have one flame height. A service man claimes this is because there is'nt enough pressure coming through the 1/2 inch copper line to use the adjustment control. I was advised to install 1/2 inch black pipe to increase the gas pressure. My city code also calls for ONLY black pipe because part of the run will be outdoors. So my question is will there be enough gas pressure if I use 1/2 inch black pipe or should I just put in 3/4 black pipe while I'm at it? I plan to tap into my indoor black pipe line at the end of a run inside my home and the whole run to the insert will be about 30 feet.