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Thread: Natural gas line????

  1. #1

    Question Natural gas line????

    About three years ago, I had a contractor install 1-1/4" polyethylene gas line for my outdoor fireplace and two fire bowls. I was unable to complete the project at that time for many reasons, but I am starting back to work on it now. I have a few questions about the gas line:

    Some of the stubs with key valves attached need to move a few inches For example, I need to move the key valve one cell over to the right in the attached image. What is the best way to do this without unscrewing/loosening the pipes from the risers in the ground?

    Is it bad to have couplings and elbows in the block for reasons such as leaks, etc.? I will need to use couplings and elbows to move the key valves. Any other ideas?

    When I run gas pipe from the key value to the inside of the fireplace hearth, do I use the green PVC coated gas pipe or flexible gas line?

    Is it common to encase the gas line in block? What if one needs to access it later for service?

    I would also like to pressure test the gas line before I surround it with block. Does 50 - 60 PSI for 15 minutes sound correct for pressure testing the polyethylene gas line? I can't remember what the contractor test it at for the inspection.

    By the way, I live in Surprise, Arizona.
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  2. #2
    Plumber jimbo's Avatar
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    Are you sure it is PE pipe? If so, the fittings are fusion welded, and you cannot touch that pipe. The green pipe looks like epoxy coated iron pipe, which is threaded like regular black iron pipe.

    Gas lines do not need to be tested to 50 PSI. The test is usually 15 PSI

  3. #3

    Question

    It is 1 1/4" PE pipe underground to the risers. The stubs with key valves are 3/4" epoxy coated pipe.

    Is 15 PSI even for plastic welded pipe (like PE)?

    Thanks

  4. #4
    Plumber Extraordinaire Pipedoc's Avatar
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    Yes. 15 psi is fine. It is okay to move the rough location of the valve through use of nipples and fittings. Just test for leaks before you cover the work.

  5. #5

    Question

    I found the inspection paperwork from the contractor who originally installed the PE gas line. At the first inspection, it failed due to improper PSI (15 PSI). I also found some other information stating that he later tested it at 60 PSI for 20 minutes. I guess that Surprise, Arizona wants fused PE gas line tested at a higher PSI????? So, last evening I retested the gas line at 60 PSI for 20 minutes. The line held 60 PSI for the required time. I left the gauge attached overnight and in the morning it had dropped to 50 PSI. Is this just due to the temperature drop overnight? I guess that I should mention that it is 160 feet of 1 1/4 gas line, so it holds a large volume of air.

    Thanks
    Last edited by figs; 06-14-2009 at 10:11 AM.

  6. #6
    Moderator & Master Plumber hj's Avatar
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    Default gas

    I am not sure where the riser is, but it should be outside the wall, not inside it. Underground gas piping, of any kind is tested to 60 psi in AZ. The PE pipe may not be fused, but could have "compression" or "slip" joints depending on the manufacturer. These are MUCH more common than fused connections.

  7. #7

    Question

    hj,

    The riser comes from underground and the epoxy pipe goes through the footer for the stub (see photo). Is it normal for pressure to fluctuate due to temperature variations?

    Just out of curiosity, why is the pressure test duration so short?

    Thanks
    Last edited by figs; 06-14-2009 at 05:36 PM.

  8. #8
    Well driller,pump repair. and septic installer Waterwelldude's Avatar
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    I don't know anything about the codes where you are, but with the pressure going down like that. I don't think I would want it in my walls.
    I would want it outside of a wall I am about to seal up.

    JMO


    Travis
    "I shall never surrender or retreat" -Col. William Travis


  9. #9
    Plumber Winslow's Avatar
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    You could have a very small leak, which is very hard to find. Testing with lbs per sq inch isn't very conclusive. I always check my gas lines with a manometer. 6" mercury on the rough and 10" or 12" wc on the finish (depending on nat or lp) after everything is hooked up on the finish. Since your local code calls for 60 psi for 20 min I would do it that way first then double check with a manometer. You know definately if you have a leak or not that way.

  10. #10
    Retired Defense Industry Engineer jadnashua's Avatar
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    Gas (air) expands and contracts with temperature...think hot air balloon - if hotter air wasn't less dense (i.e., expanded), it wouldn't float. If it can't expand or contract, it changes the pressure. So, depending on the difference in temperature when you measured, it could be entirely normal.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  11. #11
    DIY Senior Member Rich B's Avatar
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    Air pressure will change quite a bit with temperature. Use nitrogen and it should not change much if that is whats happening. It is an inert gas and used in Nascar and other forms of racing to minimize pressure changes in their tires. It is also common to use it for air tools....A tank and a way to connect it to the line and fill it is all you would need. Set the pressure to 60 and let it sit overnight again.....I drag race and have very big slicks on my car.....my air pressure is constantly changing with temps. and direct sunlight on the tires....

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    Any gas changes the pressure in a closed volume with temperature changes. Some more than others, and nitrogen isn't immune. There's always some water vapor in 'air', which can change volume quite a bit. Nitrogen is by no means inert...it easily combines with all sorts of things. 'Dry' nitrogen may be safer for the rubber, and being dry won't expand as much in temperature changes than what we call 'air', which contains a high percentage of nitrogen, but also oxygen, carbon dioxide, water vapor, and numerous trace elements along with pollution. Inert elements are those along the right-hand column of the periodic table and have 'complete' outer ring of electrons (where most chemical reaction take place - full= doesn't react). The noble gasses expand and contract with temperature change just like any other gas.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #13

    Default

    So I did find a small leak at one of the plugs in one of the gas key values (see the key valve in the photo in first post to this thread). I fixed the leak on 6/14/2009, and retested at 60 PSI. Just out of curiosity, I wanted to see how long it would hold 60 PSI, so I left the gauge attached and the line filled with air. Two weeks passed, and it was still holding 60 PSI. I forgot about it for a while, and I decided to check it again today and noticed that it had dropped to 57 PSI.This is a very small drop over a few weeks, so is this something to be worried about? I was told by the city of Surprise (in Arizona) that I must test at 60 PSI for 20 minutes. Why is the test duration so short? Do they expect the line to drop in pressure? Do the professional plumbers out there ever see this behavior? I just want to be safe!

    A few people were asking about the pipe, so I have attached some photos that I took when it was being installed.

    Thanks,
    Attached Images Attached Images   
    Last edited by figs; 07-05-2009 at 04:06 PM.

  14. #14
    Moderator & Master Plumber hj's Avatar
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    Default gas

    A natural gas line under concrete, MUST be enclosed in a vented sealed sleeve. That is why it usually comes up outside the "structure", by means of an anode protected riser, and is then piped inside the wall to the desired location. Propane gas lines CANNOT be installed under concrete at any time, or under any conditions. The test is for 20 minutes because that is all the time the inspector will spend on the job. That is also the reason you have to use a very sensitive gauge so a small leak will be readily apparent.

  15. #15

    Question

    Is what I have against code (the gas line under the footing for the fireplace)? The rough-in already passed inspection a long time ago. Since the inspection is only good for six months, I need to have it reinspected before the gas company will hook it to the meter (natural gas has never been in this gas line).

    Since the block work is underway and the inspection has already expired, I just want to be sure that all is well before I enclose the pipe in block. This project is going slow, so I am going to call for reinspection when it is closer to being complete so I don't have to keep paying for inspections. From what I understand (the information from the city), all I need is one inspection for this project (the rough-in inspection so the pipe can be covered) which already passed (but is now expired). I'm just retesting the line myself for safety and so I know it will pass upon reinspection.

    When you do backyard fireplaces, bbqs, etc., do you usually have more than one inspection for the gas line?

    I have attached a photo that shows the footing. There are three gas stubs (one on each side at the front of the footing and one in the middle of the back of the footing).

    Thanks
    Attached Images Attached Images  
    Last edited by figs; 07-06-2009 at 08:02 AM.

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