View Full Version : Gas Line Splice: How to avoid an EXPLOSION!

10-29-2007, 05:57 PM
How would I saftely cut into a black steel gas line to that I may tee off? (I'm not talking golf here)

It's a 3/4" propane gas line running overhead in attic. I have limited space to do the splice and cannot get the giant pipe cutter around the pipe. Was thinking of using a Sawzall or small disc grinder to cut through. I just don't want to ignite the propane.

Only thing I can think of is to use an air compressor and blow from the high end of the line out of the low end (having disconnected both ends of course). This is not as easy as it sounds in my situation.

Anyone have some wisdom before I use the trial and error approach? I'd kind of like to NOT singe my facial hair. :o


10-29-2007, 06:09 PM
How about turn off the gas and evac the line before you do any cutting.............

10-29-2007, 06:20 PM
He means put a vacuum to the line and suck all the gas out..lol..

10-29-2007, 06:32 PM
Blow it out topto bottem.Propane is heavy gas yes turn it it off .

10-29-2007, 06:45 PM
He means put a vacuum to the line and suck all the gas out..lol..

I actually meant evacuate the line. I'd blow it out with a compressor. ;)

10-29-2007, 06:58 PM
I actually meant evacuate the line. I'd blow it out with a compressor. ;)

That is what I ment,make sure you have NOOPENFLAMES in the house.

10-29-2007, 07:43 PM
It is not a problem once the pilots eliminate the pressure, but most areas do not want DIYers working on gas, much less propane lines.

10-29-2007, 09:20 PM
Probably will combine your ideas. Shut off Propane. Burn pilots out before sucking out lines with a shop vac. Um . . . I mean blowing top down through the main line. The compressor is probably going to do all the work though.

I've only plumbed natural gas in new construction, never spliced into a propane line. HJ is there something I don't know about propane being harder to work with than NG?

cwhyu2 stated the main difference that I'm aware of, Propane is Heavier than Air, where NG is lighter.

I think this will work dandy. If I never follow up on this thread, you all better beware of my above plans . . . :eek:


10-29-2007, 09:40 PM
If you can't get a cutter in, how're you going to get the threader in?

10-30-2007, 04:41 AM
Tell us how, after you cut the line, you are going to add a T.

10-30-2007, 05:32 AM
Propane being heavier than air is not just a throw away comment. It is the reason that a leak is more dangerous. A natural gas leak will vent through the roof and dissipate. A propane one will settle into the lowest spot it can find and accumulate there until it gets enough concentration to find an ignition point and blow up.

Ian Gills
10-30-2007, 06:43 AM
Is that why my blow torch produced some very interesting flares until I learned to use it in an upright position only?

Luckilly I was soldering outside...........naked.:)

Mike Swearingen
10-30-2007, 06:47 AM
"How to avoid an explosion"?
Hire a pro for this.
I grew up in the East Texas oil field, roustabouted in the oil field (all crude oil and natural gas) a couple of summers in college, and messed with natural gas lines of different sizes comfortably all during my younger life.
I won't touch propane (other than torch or grill). Different animal.

10-30-2007, 06:26 PM
Frenchie, I can get a little better than 180 degrees of twist or turn on a pipe wrench or hand pipe threader with no problem up in the attic. With a hand pipe cutter you have to be able to do a 360.

Cass, I'll slice the pipe, Thead it by hand (Ridged Pipe Threader) and reasemble with T, nipple and a union joint.

And a nice long pressure test with soap to make sure I don't have any puddling going on. I intend to keep this "animal" contained.

Ian, I'm NOT going to follow your footsteps with the whole "naked" trick. There's fiberglass in that attic!!


10-30-2007, 07:11 PM
Not to rain on your parade but a union may well violate code. You are probably supposed to use a nipple with left and righthand threads. Sort of a pain in the posterior but "them's the rulez."

Alternatively perhaps a shut-off valve can be used to isolate the union and make everything nice and legal.

10-30-2007, 09:37 PM
CCH, thanks for your comments. I Left-Right Nipple would do the job but you are right about the PITA issue. I'll have to double check code on this, but I was told the union would be fine. Gotta do it right . . . the first time.


10-31-2007, 05:38 AM
Ian, the interesting flame pattern is because you are getting liquid propane to the nozzle when it is inverted. That, plus any impurities it contains, can plug your filter and block the gas flow permanently. Manufacturers do not guarantee torches with a blocked filter caused by inverted use.

10-31-2007, 06:22 AM
My recommendation would be to get a small nitrogen tank to purge the line with.

10-31-2007, 12:13 PM
You realize that you are turning a half hour job into a major project, don't you?

11-01-2007, 07:54 AM
You realize that you are turning a half hour job into a major project, don't you?

You are speaking to the Nitrogen purge idea HJ? I don't think I'm going to use pure Nitrogen, but rather compressed air. Probably take me 1/2 just to get her cleared for the cut.

I wish the whole job would only take me a 1/2 hour. Probably get to it next week.