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Old 10-29-2008, 10:14 PM   #1
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General questions about natural gas fittings


How often is it safe to take apart and reuse gas fitting? Such as the connection between a gas line and the control valve in a heater?

I've noticed the mating surfaces are always flare shaped. I assume the metal is malleable and deforms to seal against the gas when the nut is tightened.

I had a plumbing teacher who dismissed this fittings as very safe, 'it's only gas'.

How tight should you make them? Hand tight, and then tighten an additional half turn with a wrench?

I assume it is not necessary to seal the threads of the nut? The gas would just escape from between the nut and the pipe anyways, right? I've never seen pipe dope on any gas valve fitting I've taken apart.

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Old 10-29-2008, 10:53 PM   #2
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General questions about natural gas fittings


I reuse them if they are in good shape. I used to just toss em but they are getting so expensive anymore.

What I look for is damage to the surface of the connection. And as always I spray everything to make sure I don't have a leak.

My buddy says I am too anal about this but I figure that if I don't have time to do it right the first time when am I going to find time to redo it later.

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Old 10-29-2008, 11:11 PM   #3
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General questions about natural gas fittings


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Originally Posted by darsunt View Post
How often is it safe to take apart and reuse gas fitting? Such as the connection between a gas line and the control valve in a heater?

I've noticed the mating surfaces are always flare shaped. I assume the metal is malleable and deforms to seal against the gas when the nut is tightened.

I had a plumbing teacher who dismissed this fittings as very safe, 'it's only gas'.

How tight should you make them? Hand tight, and then tighten an additional half turn with a wrench?

I assume it is not necessary to seal the threads of the nut? The gas would just escape from between the nut and the pipe anyways, right? I've never seen pipe dope on any gas valve fitting I've taken apart.
Gas fitters have a saying, "gas makes your house sneeze" That is usually accompanied by a picture of a house that blew apart. Gas is nothing to play with if you are not experienced. I do not like to re-use flex gas hoses, I have had them break. When I do re-use them, I inspect them carefully for breaks. I use leak detector on all gas fittings after I turn on the gas. I also smell the fittings. You usually cannot hear a gas leak. I also use a bit of pipe lub on the flare fitting, not much, just enough to see. Too much can get into the piping & cause problems. I cannot tell you how much to wrench past hand-tight. After you install enough, you get a feel. The seal on the gas flex is the flare fitting, not the threads.
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Old 10-30-2008, 10:57 AM   #4
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General questions about natural gas fittings


Thank you for your replies.

Replacing flexible gas connections sounds like a good idea. I always replace the supply line when I have to replace a fill valve on a toilet, why not the supply line for gas? I wonder how expensive flexible gas lines are.

I like to use the soapy water test. Should the mix be 50/50 soap and water?

I do inspect the mating surfaces. From what you guys have told me, if the mating surface looks good its probably okay to reuse a fitting three or four times.
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Old 10-30-2008, 11:45 AM   #5
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General questions about natural gas fittings


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I like to use the soapy water test. Should the mix be 50/50 soap and water?
Yes 50/50 should work. I like using liquid laundry detergent because its high soap concentration seems to guarantee you get more than enough soap. Plus you're usually not far from the laundry facilities.

Last edited by dac122; 10-30-2008 at 11:48 AM.
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Old 10-30-2008, 04:39 PM   #6
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General questions about natural gas fittings


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I do inspect the mating surfaces. From what you guys have told me, if the mating surface looks good its probably okay to reuse a fitting three or four times.
There is a limit to reuse. The more you flex it the more it could go bad.

Besides the soap test I also do a meter test to see if there is anything moving through the system. The 1/2 gauge should not move at all in 15 minutes. If you really want to be safe then let it go for an hour. Make sure there is nothing else on that would use gas. I usually shut the valves of other gas appliances to make sure no one turns them on which would make the meter show gas passing through.

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