Hi Caspian,

Yes, it's true that you need to look at the spec sheet/install guide to verify that you have the correct size gas pipe.

Although I didn't have to upgrade, my contractor did verify the size of my existing pipe with my Wolf spec guide as one of the first orders of business.

I've read on this forum that insufficient gas supply can lead to poor burner performance (gaps in the burner flame), etc.

I'm confused. What is your situation? Are you definitely getting tankless? Definitely getting a pro-style range? Trying to decide if the purchase of one will affect the other?

A number of years ago, I put in a 175,000 BTU/hr tankless water heater, and I located it under my kitchen. I put in oversized piped (1") that would be able to handle both the water heater and an eventual pro-style range. The run from the meter is about 30', with minimal elbows (2 or 3). I did the calculations at the time, but don't recall the details. The upshot was that 3/4" was marginal for me, and 1" provided a comfortable margin.

Most high end ranges require 5/8" or 3/4" flex connector from the wall to the range. What diameter pipe is necessary to get from the meter to the connection point depends on several factors including distance of run, input pressure, branches and elbows etc. Whole house tankless water heaters run about 200 MBH (200k BTU/h) and would require a dedicated 1" line to run about 50-70ft using standard IP. In my house, there was an existing 1" line that fed a standard water heater and a furnace. When we redid our kitchen, my builder was originally planning to branch off of that line but I pushed him to upgrade with another 1" line off the meter that ran to the kitchen and 1/2" branch for a future fireplace. Keep in mind that a 1" line is approx the equivalent of 4x 1/2" lines so it's a lot cheaper to run a larger diameter line than to run multiple equivalent lines assuming location of your appliances are near or inline with each other.

Not sure what you have today so can't judge if what your sales guy is quoting but I will say that most houses are under spec for running a high power range plus a furnace and a water heater. Add to that your desire to go tankless, I would expect that you will definitely need to upgrade your gas service.

For point of reference, a 4 ton furnace is 48 MBH, standard water heater is 40-60 MBH, a 36" high power gas range max about 180MBH, and a tankless water heater is 200MBH. Now you are unlikely to have all of your burners on max and the oven on at the same time so assuming your existing line is 1" and services the range and the furnace and is less than around 80 feet long, then you should be ok for the range and furnace. Then you can simply run another 1" line direct from the gas meter all the way to your tankless water heater. You might not need a 1" line if you are locating the unit close to your meter. Alternately, if all of this is new construction, then you can run a single 1.5" min (I would go 1.75-2") line with sufficiently sized branches for each of the appliances.

Hope this helps and good luck.

If wondering about your gas meter a quick call to your gas company can clear that up. Simply tell them your target BTU/hour consumption and they will tell you if your current gas meter (they should know what it is) is up to the task. If not, they will let you know.

When I installed my range I had to get a new gas meter. Kind of cool to have the "big guy."

-Stooxie