Gas Piping Size - Inner or Outer Diameter? (Post Moved)

Old 08-21-06, 10:47 AM
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Gas Piping Size - Inner or Outer Diameter? (Post Moved)

Hi There

I need a little help here. I bought a second hand gas stove, a "professional" model that needs the larger piping because of the burner output. I told the gas guy I hired I needed that, he seemed to know what I was talking about and said he always used the larger pipe, so the stove was installed.

I haven't had a chance to use the stove yet (renos, the rest of the kitchen isn't ready), but when I was downstairs, I saw the gas piping and it looked the same size as all the other pipes. Reading the manual for the stove it says it needs 3/4" pipe. I asked a plumber who was over what size pipe it was and he told me it was 1/2".

So I called the gas fitter and he blew up on me, saying that the plumber "only knew that sh@# runs downhill", and tells me that he installed 5/8" pipe, but the plumber would see it as 1/2" because plumbers always talk about inner diameter, while gas guys use outer.

Is this right? I would have thought that copper pipe was copper pipe was copper pipe. But then again, I'm new to all of this. The guy further said that the 3/4" specification doesn't matter because they're being conservative without knowing the run distance. He said under 60 feet in 5/8" should be enough for up to 60,000 BTU, which I think is about right for the stove.

Am I being screwed here or is the guying telling it straight? Anyone?

Old 08-21-06, 01:41 PM
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bgreenhouse, Welcome to the DIY Forums.
I guess maybe I am behind the times. I have not seen copper run for a gas line inside the house unless it was an LP gas line run with soft copper. 5/8" is also what I consider refrigeration tubing. I may be all wet. Call your local Plumbing Code office and ask what the regulations are where you live. Not running the size pipe the manufacturer recommends also voids any warranty you have. Good luck.
Old 08-22-06, 03:54 AM
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There are several thing I would like to comment on here.

First, line size and material. Copper tubing is usually measured outer diameter(OD). Copper pipe, along with iron pipe or stainless steel tubing are measured usually inside diameter (ID).

If copper was run for the gas line, it needs to be copper tubing with flare connections if local code allows, there is no place that I know of that rigid copper with sweated connections is acceptable. The biggest issue with copper tubing is per NFPA, it can not be concealled inside walls or ceilings.

If you were told it was 5/8" OD copper, chances are it's tubing. 5/8" OD copper tubing will provide 78,000 BTU's at 60 feet. If your range has a rating of 60,000 BTU's you should be ok. Just to note, 5/8" OD copper tubing is significantly smaller than the called for 3/4" ID pipe. I would have been more comfortable if he ran a minimum of 1/2" ID pipe (larger than the 5/8 copper run, still smaller than the 3/4). Now that I've likely confused you let's look at your specific set of circumstances.

If the manual calls for 3/4 inch ID (I've seen many that do) this is usually a generic number. It may or may not be an issue for warrenty coverage. Being said that this range is second hand, I wouldn't be concerned if you don't have 3/4" pipe.

I would be concerned that you have enough volume (BTU's) of gas feeding the range. You need to know the total BTU's the range requires (it should be in the manual). If it's a "professional" model GE or Kenmore 60,000 BTU's sounds about right, 70,000 is probably more acurate. If it's truly a profession model such as Viking, Dacor or Garland , I'd double that number to 120,000 - 140,000 BTU's.

Are you running LP Gas (propane) or Natural gas? This needs to be determined to properly size the line. Natural gas appliances operate at lower pressures than propane.

For 5/8 tubing at 60 feet will supply 78,000 BTU's of propane. This would be marginally ok for your situation, but doen't leave much room for error. I would have gone a mimimum of 1/2" ID pipe or CSST.

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