Purging natural gas lines of air.

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by ario, Oct 21, 2004.

  1. ario

    ario New Member

    Messages:
    9
    I had the gas turned off for a month and removed the line to the gas dryer (we're going to electric) and plugged the pipe. Also installed new hot water heater. I can't light the pilot off course because there is air in the lines. How do I safely purge this air? Thanks.
  2. LonnythePlumber

    LonnythePlumber Plumber, Contractor, Attorney

    Messages:
    319
    Location:
    Wichita, Kansas
    Continue to Hold

    The safest way is to continue to hold the pilot buttom down and bled the air through the little pilot tube. Three full minutes should purge your line. You could also apply a continuous flame to the thermocouple allowing you to bled the air through the gas valve but this results in burnt eyebrows and mustaches sometimes. You could also disconnect a pipe at the union or flex connector but your must recheck that there are not piping leaks when you reconnect.
    I would just be patient and hold down the button.
  3. rbarrett

    rbarrett New Member

    Messages:
    2
    I have a natural gas line that was run from my house to my shop around two years ago. I have recently installed a heater in my shop therefore connected my gas line to my heater. When I turned the valve on at my house I heard the gas flow into the line. I tried to light the pilot but was unable; I then disconnected the gas line to the heater and never smelled gas! I could put my thumb over the end of the line and hold it for a few seconds and then remove it and could feel pressure but smell nothing! I also let the gas run 10 minutes or so and never could smell gas?? Any ideas would be greatly appreciated..

    Thanks in advance,
    Confused
  4. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    You can only run gas pipe so far and have it work properly, but it should still run enough for it to "smell". How far is the total from the curb to house to garage?

    Was the pipe capped very well the entire time? Maybe it is plugged with rodent, dirt, debris or water. It might take high pressure air to clear the pipe.

    Did you do any digging in the area since it was used? It could be broken. If the pipe is iron it could have rusted through.

    NOTE IMPORTANT: A pipe, even plastic abandoned that long should be tested by a licensed service person before it is used, not a DIY project.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,247
    Location:
    Cave Creek, Arizona
    pipe

    You can run a gas line as far as you wish to and it will still flow gas. If the line is too small for the length, the burner will not operate properly, if at all, but there will still be some gas coming from the pipe. If the line has an obstruction, you have to find out how it got there before you do anything, especially using high pressure air.
  6. construct30

    construct30 New Member

    Messages:
    590
    Location:
    NorthWest PA
    I don't think a see snake will fit in most gas pipes so how are you going to find what's down there? I've seen gas line service men use air to clean pipes.

    I should add be very careful and don't have someone looking down the pipe when you do it. Did you ever shoot a high powered air gun?

    Also I said work properly.
  7. rbarrett

    rbarrett New Member

    Messages:
    2
    Thanks for the replys! I figured it out:) when i would turn the gas valve on in the shop it would make a pop sound which was triggering a check valve in the flex line I had purchased from lowes! I turned the valve on real slow and it started to flow at a higher rate in which I then smelled gas! So everthing is working! Thanks again guys....
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