This question comes up a lot when we are quoting jobs that other plumbing companies have already quoted. Prospective customers are often told that their gas pipe sizing is undersized and that it will need to be increased. This of course adds “thousands” to the quoted price for a supposed “requirement.” Well, that is simply not true in the vast majority of cases. In fact, it is VERY rare that the gas pipe sizing needs any work other than what is basic and included in the normal price. We know this for a fact, because despite our small size, we retrofit install more Navien tankless water heaters than any other residential service plumbing company in the area. We know based off purchase records from the area suppliers. So, if Navien is the #1 bestselling tankless water heater brand in North America and we purchase more than any other plumbing company, then we obviously have a lot of tankless units throughout the area. In the last few years, we have installed over 400 Navien tankless water heaters and probably quoted over 500. In all, there has been less than 10 times that the gas pipe sizing needed to be increased. In fact, it is far more common that the gas meter size needs to be increased, and the utility provider does that for free. If you need more proof that the company that pays their employees on 100% sales commission might be trying to pull a fast one to drive your overall ticket up; go to the Navien website and read for yourself. It clearly states on the “Navien NPE-240A2 Features & Benefits” (one scroll down on the bottom right); “1/2” gas pipe capability up to 24 feet. Cuts installation time. No need to install new gas lines for retrofit installations."