My plumber has extended a 3/4" black iron gas line that originally supplied just my stove cooktop to a future for a fireplace. The total run is 45 ft of 3/4", reduced to 1/2" after a two separate tees that then feed up about 3 ft to the two fixtures. The stove is only gas for a cooktop (oven is electric - dual fuel stove), and I estimate the cooktop burners max out at 36K BTU if they are all on at the same time (probably a very conservative estimate). The fireplace maxes out at 26K BTU. The plumber seems to think this 3/4 inch supply over 45 feet is plenty to serve the cooktop and the fireplace, please let me know if anyone disagrees. My primary question is whether we could continue the run to terminate outside to the deck of my house, extending the run to about 60 feet total, and then provide a supply for a natural gas grill, which would pull at most 100K BTU (probably less). My plumber is having a really hard time figuring out if the supply is sufficient to do this, not sure why. Can anyone help? I'm in Massachusetts, which is a little over the top with code compliance, and want to make sure I have my ducks in a row as I need to close up my basement after this job is done, which would make any retro fixes a major hassle.