I have a gas insert fireplace. At the end of last winter, I shut off the pilot and closed the valve on the insert. I also closed the valve in the basement that feeds the lin going to the insert. The basement valve is about 30 linear feet away from the fireplace, and there are no other appliances between the basement valve and the fireplace.

This fall, I turned the valves back on, then tried to light the pilot on my fireplace again. I had to bleed air out of the line for about three minutes before the pilot on the fireplace would light.

Does this mean there is a leak in my gas line between the basement valve and the fireplace? The fact that I had to bleed the line for so long before gas came out again suggests that it had filled with air during the summer. If the valves on both ends of the line were closed, I don't see how this would have happened.

On the other hand, I don't fully understand how gas works. Could the gas that was left inside the line have "gone bad," or something like that, over the summer, causing me to have to bleed it all out until fresh gas reached my insert?

The line is CSST, by the way. There are no obvious leaks (I did the soap test on the joints), and I never smelled any gas in my basement over the summer (but I was not there every day).

  • Do you have LPG or natural gas?
    – Kris
    Sep 25, 2018 at 21:13

1 Answer 1


3 minutes is really not that long the regulator had to fill the control after its valve and to the pilot if you had a leak 30' away it would have taken much longer, gas lines after the main gas regulator are only approx 3/4 of a psi, very small so it can take a little time to fill. The way gas lines are tested where I have installed them is by pressurizing the lines with the local shutoff at the stove, fireplace, furnace turned off and the line pressurized up to 30 psi, the inspector notes the pressure then inspects the work if the gauge drops you fail. We usually do this pressure test the day before inspection and make sure there is no drop overnight, not just the 15 -30 minutes the inspector is there.

  • +1 exactly right. There is no expectation for the system to be utterly leak-tight anyway, otherwise they would make the pressure hold overnight (or over several days) during the test. Sep 26, 2018 at 4:48

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