gas line pressure test


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Old 06-20-10, 02:22 AM
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gas line pressure test

hi guys,

a gas fitter just installed a gas line in our home for a range and bbq. He pumped up the line to 15psi of AIR last night. Tonight i went to check the gauge and it was at 10psi. It held the 15psi pressure for a couple of hours so I am not sure if I have a leak somewhere or if its due to temperature variation. Have you guys had this happen to you?

The inspectors in my city only perform a 15min test with 15psi and make sure it holds pressure. It will pass inspection but I am concerned that there might be a leak. Our gas line pressure is just under 2psi. I don't have a pressure pump so I will see if it drops below 10psi tomorrow. It it does I am thinking i do have a leak somewhere.

Sorry guys, I am just a noob. Look forward to hearing from yall.
 
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Old 06-20-10, 10:59 AM
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Gas Test

>>>a gas fitter just installed a gas line in our home for a range and bbq. He pumped up the line to 15psi of AIR last night. Tonight i went to check the gauge and it was at 10psi. It held the 15psi pressure for a couple of hours so I am not sure if I have a leak somewhere or if its due to temperature variation. Have you guys had this happen to you
 
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Old 06-20-10, 03:22 PM
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Thats a common problem if you charge the line when the outside tempeature is 80 or so and it starts to drop as the sun goes down, I don't think you have any problem.

Thats why I liked the old mercury gauges (they don't allow them anymore) they will tell you instantly when you hook them up if you have a leak. [/QUOTE]

Thanks for the feedback on this. I checked again and its now at 9psi. Can the temperature really cause this much of a pressure variation?
 
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Old 06-20-10, 03:58 PM
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If the ambient temperature has returned to what it was when the line was first pressurized then the pressure should have returned to the point it was at when first pressurized. If the temperature has only gotten colder since the initial pressurization then it is possible that there are no leaks IF you have a lot of fairly large piping. Personally, I would be concerned about a 30% drop in pressure over a 24 hour period depending on the size and length of the piping.

I had a small system that lost pressure at an alarming rate when first tested and I found the (brand new) valve at the end was defective. When I plugged the outlet the pressure held fine for the official inspection and then I replaced the valve.
 
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Old 06-20-10, 11:34 PM
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Originally Posted by furd View Post
If the ambient temperature has returned to what it was when the line was first pressurized then the pressure should have returned to the point it was at when first pressurized. If the temperature has only gotten colder since the initial pressurization then it is possible that there are no leaks IF you have a lot of fairly large piping. Personally, I would be concerned about a 30% drop in pressure over a 24 hour period depending on the size and length of the piping.

I had a small system that lost pressure at an alarming rate when first tested and I found the (brand new) valve at the end was defective. When I plugged the outlet the pressure held fine for the official inspection and then I replaced the valve.
yes the pressure drop is concerning. I will get the gas fitter to check for leaks and test again. The piping is 3/4" and there are two runs, one is 20ft and the other is 40ft. When he first pressured it up, it was cold day but it has been warmer now. The pressure has been sitting at 9psi for around ten hours now. I will check in the morning again to see how much its lost.
 
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Old 06-21-10, 01:02 PM
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Gas Test

Furd is correct, if the pressure dosen't go back up as the temperature nears its original point and keeps dropping, there's a good chance you have a leak.
 
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Old 06-22-10, 09:24 PM
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Originally Posted by shacko View Post
Furd is correct, if the pressure dosen't go back up as the temperature nears its original point and keeps dropping, there's a good chance you have a leak.
The gas fitter came and tightened the joints. The inspector came and passed the inspection. However, i told the gas fitter to leave the pressure gauge on. I again checked the gauge 24hrs after and it dropped to 9psi. I talked to the gas fitter and told him about this again and my concern about a leak and his answer was that the city only requires the pressure to stay at 15psi for 15minutes and not 24hrs. I think thats pretty absurd and am concerned about a gas leak.
 
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Old 06-23-10, 12:50 PM
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Did the pressure go back up when the temperature started to climb? if so you are probably o.k.
 
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Old 06-27-10, 09:30 PM
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If you're testing against valves, remove the valves & just test the piping (cap the pipe). I've left tests on for months that held.
 
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Old 06-28-10, 11:27 AM
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Gas Test

Originally Posted by steve_gro View Post
If you're testing against valves, remove the valves & just test the piping (cap the pipe). I've left tests on for months that held.
steve_gro: I don't know what part of the country you work in but, the areas I'm familiar with require the test to be thru the valves; capped at the appliance.
 
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Old 03-17-11, 08:13 PM
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Post Testing through valves

Hi guys.
It is in the nature of valves that they will leak a minute amount of gas because of movable parts. At least today's valves arent as bad as the old grease valves that had to be cranked down on just to hold 10lbs for 15 minutes.
The 9lb resting measurement of the installation in question is probably the limit of the valve and is well above what is needed for the Utility to hook up. He should not worry about it.
 
 

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