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 residual gas in disconnected gas pipes
Author: xtinehpgh (PA)

Just bought a 100-year-old house. Capped off gas lines from old gas lighting fixtures are sticking out of the baseboards in several of our rooms. The lines are still active, we just found a plumber who will be disconnecting these unused gas lines so they are inactive.

My fiance wants to remove the portions of pipe sticking out of the wall once the lines are inactive. He had always intended to do this part himself...when I mentioned this in passing to the plumber, he said there was no way he would do this. He said if we do it, then we'd still need to cap off line because of residual gas.

It would be very difficult to cap off the line after cutting it so its not sticking out of the wall... we'd have to remove the baseboard and possibly some of the drywall to be able to access the pipe where it terminates behind the wall to cap it off.

I also read online that you aren't even allowed to cap off a gas line behind a wall!

Isn't there any way we could legally and safely accomplish this? All that would be in the line is residual gas leftover from before he disconnected it. Couldn't we just open a window in the room and fan the residual gas out the window?

I appreciate any advice here because now I am scared to mess with these old abandoned pipes.

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 Re: residual gas in disconnected gas pipes
Author: stuckinlodi (MO)

After the lines are disconnected from the gas supply I'd uncap each end of the dead lines and then blow air thru them from the other end. Probably better to blow the air into the pipes from where they are disconnected (basement, crawlspace, etc). That way any residual gas would be blown into the various rooms and as you said you can open windows to dissipate any fumes. You can get a length of flexible hose or plastic tubing and connect it to the end of the pipe in each room and run it to a nearby window so the fumes go outside, or even do one pipe at a time so you only have to get one length of flex hose. Let the air blow thru the pipes long enough you are confident it is purged.

Depending on the length of the old pipes there could be enough gas to flash, so no smoking or open flames in the area when doing this. Just use common sense and assume there is some residual gas present. After purging the old pipes then you can cut them as needed. When old homes are remodeled or torn down this is done all the time.

Edited 5 times.

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 Re: residual gas in disconnected gas pipes
Author: packy (MA)

I wouldn't worry about residual gas. there isn't enough to even ignite. especially if it is open on the other end.
remove the stub outs, make the hole bigger (you have to patch it anyway) and screw a plug into the fitting behind the wall

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 Thank you both so much. :thumb:
Author: xtinehpgh (PA)

Thank you both so much for your replies - now I can stop obsessing and worrying. I had thought about using a hose as you mentioned.

Edited 1 times.

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 Re: Thank you both so much. :thumb:
Author: stuckinlodi (MO)

packy is a real plumber with decades of experience, I'm just a wanna-be do-it-yourselfer, so his advice and assessment is much more valid. But I thought if you went to the extra effort to purge the old gas pipes with air that you'd feel better about it and that peace of mind is worth something. A lot of people are extra-concerned when it comes to gas so if you can do something to reduce that worry I'm all for it. Plus I didn't know how big your house is or how many feet of old gas pipe you have and if there could be some trapped gas in there for awhile since it would rise to the upper ends of the capped pipe (natural gas rises, propane settles to lower areas)

Edited 2 times.

Post Reply

 Re: Thank you both so much. :thumb:
Author: xtinehpgh (PA)

The pipe in question originates from our basement and goes up two floors to our bedroom. So since it might be longer than people were thinking and because I'm paranoid about natural gas, I will probably at least try to vent the residual gas out a window with a tube or hose or something like that.

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