Natural Gas Piping Pressure Test

Hello,
All the instructions I have seen for doing a pressure test on new natural gas piping say to disconnect the meter, all appliances and all shut-off valves and cap the ends of the lines. What is wrong with just leaving the shut-off valves in place and turning them off? Local code requires a pressure test of 10 psi for 15 minutes, and the WOG ball valves I am using are rated to 600 psi (and tested to 100 psi). So they should handle 10 psi!
Thanks, Wayne
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Wayne Whitney wrote:

By doing it the way they say you are checking pipe & pipe joints in inaccessable areas. A leaky valve can be easily replaced but a leaky joint in a wall or slab cannot. You have to start with what you *know* is good, then eliminate other sources. Doing it their way is establishing a "known" good.
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A new installation would not have any appliances, or shut off valves installed cause your in "rough in stage" Nor would the pipe be covered up. So finding a leak is easy.
Where I live gas lines are tested at 30 psi for 24 hours.
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Thanks for your response, that makes sense for new construction. I happen to be remodeling, plus all my pipe is accessible since my house is one story over a crawl space.
Now I understand that the rough-in gas pressure test is done with the meter disconnected. When using rigid pipe for gas, how is the final connection at the meter usually made? A union? The meter should be in an exposed location, so a union should be fine.
Cheers, Wayne
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Capped ends seal better than valves. You might get some miniscual leak through a ball valve which would cause the pressure to drop over the duration of the test. Capping the valves avoids the possiblity of getting a false fail.
The operating pressure and test pressure of natural gas are so low that you will never break a valve or pipe from overpressure.
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Thanks for the response. It seems like it would be fine to test with shutoff valves in place, the valves turned off, and the downstream end of the valves open. Then if there is a slow leak, first check the valves by plugging their downstream ends.

Yet I understand the test pressure can damage the meter. So is a 600 psi WOG ball valve just after the meter sufficient to safely isolate the meter?
Cheers, Wayne
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Wayne Whitney wrote:

No. The pipe being tested must not be connected to the meter in any way. I am surprised that you even have a meter. If you are doing this much remodeling, I am surprised that the gas company did not come out and pull the meter.
You can put a valve in the line after it has been tested, but not to isolate the test from the meter.
--
Robert Allison
Rimshot, Inc.
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Thanks for the definitive response. Since the meter must be disconnected at the time of the test, it would be standard to use a union at the meter to make up the connection after the test?
As to my remodeling, I am replacing all the gas piping, but we are currently living in the house. So I'm going to run all the new pipe, pressure test it and get it inspected, then switch over the meter outlet and appliances to the new pipe.
Thanks, Wayne
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wrote:

Another reason not to permit shutoff valves for testing is that if a valve should leak slightly you will likely overpressure and ruin any gas control the valve shuts off, including the meter. It wouldn't take much leakage and the gas company would not be happy about that.
I think all or nearly all meter connections have integral unions for removing and installing the meter.
Don Young
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Wayne Whitney wrote:

It is standard to bring your pipe to the meter location, then (after testing and inspections) the gas company will make the connection from their meter to your pipe. Although it involves unions, it is probably not in the way you are thinking. The meter itself has a union type connection on both sides. The gas company will remove the cap or test cap from your pipe, install the piping needed to attach to the "out" side of the meter and install the meter. This does not mean that you can just run the pipe out of the house just anywhere, it must be close to the meter location (since you have an existing location).

Got it. What you should do is call the gas company and ask them what they want. They are usually happy to come out and tell you.
--
Robert Allison
Rimshot, Inc.
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