Robert: Thanks for your note. My comment was for the Model 106A. And you are correct about the specifications listed in the manual.

Here is the skinny on my comment. As you state, the requirements are for a 1/2-inch NPT [National Pipe Thread]. and, if you hard pipe the gas supply in 1/2" pipe all the way through to the heater, you are golden.
However, what often happens is that the hard pipe is brought up to the heater and a valve is installed, and then a flex line is used to make the connection into the heater from the valve. Makes it easy to make the final connection and to disconnect the heater from the gas supply, when necessary. Often, I will use a BrassCraft flex line, like one might find at Home Depot or Lowe's. However, the nominal 1/2" BrassCraft flex gas line has 1/2" fittings on the ends, but the flex line is just 3/8" in diameter. Even at a short distance of just 12 inches, the BrassCraft 1/2" flex line has a maximum capacity of 102,000 Btus, which is less than the rated capacity of the heater. Perhaps I was not specific enough in my earlier post. My intent was to say that it is imperative that any flex line be appropriately sized to meet the capacity of the heater. When considering BrassCraft flex lines, you need to use a 5/8" nominal flex lines, as they use a 1/2" flex conduit and will convey sufficient natural gas to the heater

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• Steven G on Feb 24, 2017