Can someone explain to me what the issues are here? Is it really necessary for me to swap out my current gas line with something different in order to install a new dryer?

T&Pvalvereplacement

I just hooked up a new gas heater and dryer. There were no issues before, and yes, my home was built in 1920, so, I purchased 2 ft. of flex line and hooked up both to the main gas. I ran a test on everything and wala!...no problems. But, it's your decision.

Agreeing with most of the comments : It is known that hydrogen sulfide corrodes copper , I believe there were traces of H2S in gas one hundred years ago, today there is "none". Mercaptan odorant contains sulfur but it does not corrode ( although shyster lawyers file lawsuits on that basis). So , legislators , being technically ignorant ,often outlaw copper for gas lines on the basis of what their grandfathers told them. Bottom line , copper is safe but often against the law. Copper is not subject to stress corrosion cracking in H2S. Ammonia ( in many house hold cleaners) will attack copper and brass. With much the same reasoning galvanized steel is also often not permitted for gas ; black iron is the standard.

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Now, I would have replaced the soft copper anyway because it wasn't a good fit and I would have had to bend it more. I didn't want to mess with a possible kink or stressed connection, but even if I wanted to use it, I'm not sure if I could have found the parts/fittings to make it happen.

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Just purchased a new dryer, and when it was delivered the installer said he could not connect it to our soft copper gas line -- he said it needs to be replaced with another type before he is allowed to touch it. He also said that any appliance installer would have the same policy. He did say, though, that we can connect it ourselves to the current line if we want to.

Some years ago, the use of flexible copper lines were frowned upon by all the gas line governing bodies. Everyone did it this way but after a few of the lines broke, came loose or just leaked due to a poor work ethic, most governing bodies said no to soft copper lines. Now you have to use (buy) an approved gas connection line before any licensed contractor or service company will work on these units. You can thank big brother.

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IFGC 403.4.3 Copper and brass. Copper and brass pipe shall not be used if the gas contains more than an average of 0.3 grains of hydrogen sulfide per 100 standard cubic feet of gas (0.7 milligrams per 100 litres). Threaded copper, brass and aluminum pipe shall not be used with gases corrosive to such materials.

However, our gas utility forbids it under all circumstances. If they perform an inspection and find any kind copper line they will not provide service. Doesn't matter if the house was built in the 1920s or it would a major inconvenience for you to replace. It has to go and my City has no authority to demand you get such service.

The ICC Fuel Gas Code, doesn't forbid the use of copper gas lines. And for that reason the jurisdiction I work for does not forbid it currently.

T&Pvalvewater heater

Another thing is that gas comes usually from various sources and therefore the quality of the source might not be uniform. So some areas might have too much hydrogen sulfide in the gas, making it corrosive to the copper lines.

Sounds like a liability issue. If they hook it up and the line breaks or leaks, they can be held liable. They probably want a gas flex line (something like this) installed between the copper and appliance.

The existing line is probably a thinner type "M" copper tube line that is used for water only. It will work for NG and LP, but ii is not really made for a gas application. The copper line needed for gasses application is "L" type copper tubing. It is thicker walled and flexible.

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So as @Machavity pointed, out it is probably a liability issue. The installation tech doesn't know the quality of the gas line considering the potentially but perhaps minor risk that the gas quality is poor.

If I were you, I'd get a gasfitter out to have one installed and hook up the appliance (which means future deliverers will install it). You don't want to be wrong on a gas line.

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This started as a comment and got long. I do agree the "real" reason is because the legal/governing bodies say so, but there's also a defacto reason:

T&Pvalvedripping

I think the big reason the gas company doesn't like copper pipe is that it is soft enough you can drive a nail through it. And depending on the installation practice of owner, it might not be easily identified between gas or water lines.

I just installed a water heater in an older home, and I had to replace the gas valve as well as the soft copper pipe because they no longer make any fittings for the old valve or copper that was there. So, your copper might not have a fitting that is compatible with the dryer and you might not be able to find an adapter.