acceptable pressure loss in black pipe

[Joe Cullin]

We're having a fireplace insert installed, so we had a plumber install a new natural gas line (black pipe), about 35'.

They put a pressure gauge on and pumped it to 15psi. The next morning the inspector came, and it was down to 2psi.
We've had the plumber come back twice since then. The first time, they found a problem, but it still lost 10psi over 24 hours. This last time, it held at 15 for a few hours. It dropped to 12 by the next morning (20 hours) when the inspector came, but the inspector passed it.

That was 4 days ago. It's down to 5psi now.

The fireplace installer is coming in a few days.

Do you think I should leave "well enough" alone, or should I call the plumber to see if they can find any other leaks?

 

[Lightningwill]

Was the gauge continuously reading over these extended time periods? Or was the gauge valved off except when readings were taken? I ask this because the gauges themselves can be leaky. Not necessarily a problem if you're reading it after 15 minutes, but can be over longer time periods.

 

[Sponsor]

 

[Joe Cullin]

I've left the gauge attached, with the shutoff valve next to it open.

Since the most recent fix, here's what I've recorded.

- 15psi Thu 11:15am
- 15psi Thu 12:15pm
- 15psi Thu 1:30pm
- 14psi Thu 7pm
- 12psi Fri 7am
- 11psi Fri 6pm
- (I was away for 3 days, with the heat off, and it finally turned from summer to fall weather, probably a 15–20 degree temp drop inside.)
- 5psi Mon 4pm
- 5psi Tue 11am

So it sounds like I should chalk it up to the gauge itself. Just wanted to run it by someone other than our plumber. My confidence was a little shaken by them needing 3 trips to get it right.

 

[John Gayewski]

Don't test for more than 15 min. The gauge should be a 15lb gauge and be set at 10 psi. This will show a leak, being the increments area so small. Anything other than this is unreliable due to temp changes and pipe expansion and contraction. If the pipe is hooked to the rest of the system without being valved off the test is not reliable.