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I'm planning to add an appliance to my house, and will want to do a pressure test of the newly installed gas lines. My main shutoff says 175 PSI, but most of the appliance valves say either 1/2 or 5 PSI. Finally, I see a Nibco valve at my local hardware store GB1A-3/4 that lists three different pressures: 1/2, 5, and 600 PSI CWP.

For the nibco valve, does that mean that it would be able to withstand up to 600 PSI of (cold) air/gas pressure, but should only be used as a main shutoff for up to 5 PSI, and an appliance shutoff where the working pressure is less than 1/2 PSI? Should the other shutoff valves rated at 1/2 or 5 be able to withstand the 4 PSI of the pressure test?

I plan to do the pressure test at about 4 PSI, with a gauge that reads up to 15 PSI. Should I cap off the lines before the shutoff valves (to avoid stressing valves, but not test them), or close the shutoff valves and remove the caps on the traps so that excess pressure leaking through valves would be vented instead of damaging the appliance regulators.

My house's regulator is set at 7" of water column, gauge pressure, and I need to test at a minimum of 3 PSI-gauge, and I'm located in Indiana, United States.

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I'm of the mindset that gas is something best left to a licensed professional. If you don't know the answer, don't do it. This is not a DIY project. – Chris Cudmore Jan 29 at 21:26
DIY on this is a really bad idea. It's not the pressure testing, but the quick dismissal of minor pressure loss in the "it's good enough" mindset that is potentially deadly. – Fiasco Labs Jan 29 at 22:17
I completely agree that a dismissal of minor pressure loss is dangerous. That's why I want to perform the proper testing. In fact, I'm paranoid about the lines from the shutoff valve to the appliance because they are unable to be pressure-tested (though they can and will be leak-checked with a commercial leak-testing liquid). – Pigrew Jan 29 at 22:27
Why can't you test the lines from the shutoff valve to the appliance? – Philip Ngai Jan 31 at 1:46
@PhilipNgai, because I need to test the newly installed pipes between my main shutoff and my new appliance. I'm replacing an electric range with a gas range. I needed to run new pipe from existing gas pipes to my kitchen. Also, my furnace is hard-piped, which also complicates matters. For the appliances with CSST, I plan to cap them off at the end of the CSST. – Pigrew Jan 31 at 5:39
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I'm not quite sure exactly where you are proposing to cap off the lines, but if you add a valve to supply the new appliance, you need to test every new connection you make.

If your work is located in an area that is easy to inspect and you get a permit and have your local city inspector sign it off (assuming owners are allowed to do this kind of work) you should be reasonably safe but of course I assume no liability for anything that happens.

It does sound like you've carefully studied what documentation you can find. Here's a description of the standards applying to the valve you wish to use.

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I propose disconnecting all of the appliance connections and then appliance valves, and then putting on a black iron "cap" fitting that looks like (plus closing the main valve on the house side of the meter). The other option was to leave everything in place except removing the cap from the traps so that when the valve leaks, the pressure would not be applied to the appliance. The link that you sent doesn't cover the CWP rating? Can I use that (or the WOG) rating as a limit to the test pressure applied to the valve? – Pigrew Jan 29 at 22:19
Here's a description of CWP vs WOG: CWP stands for Cold Working Pressure, and is an indication of the pressure rating for piping, valves, and fittings at a temperature range of -20 to +100F. WOG (Water, Oil, Gas) is an older standard that never applied a maximum temperature requirement. As is apparent, higher temperatures can significantly degrade pressure handling in piping systems. Thus, CWP is the preferred standard for communicating a fitting or valve's rated capacity. – Philip Ngai Jan 30 at 16:35
I see what you mean. It would have been more clear if you had included the (assumed) step of closing all the appliance valves too. Your valve's CWP rating is much higher than your proposed test pressure, isn't it? I think that I personally wouldn't disturb so many connections and simply close all other gas valves for the test. When I built my house, I think my plumber tested the gas system at much more than 4 psi, perhaps around 15 or 20. Why not call your inspection dept and ask them? – Philip Ngai Jan 30 at 16:42
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A liquid leak test (try Abbey leak detector or Sherlock Leak detector) is a more appropriate test for gas connections by a consumer.

Also know this, the gas pressure inside the house is low, around 3 PSIG. The gas meter contains a regulator to reduce gas main pressures.

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I used to work for the gas company and I used to use water with some dish soap to check for leaks. You will see small bubbles at even the slightest leak. However, I was installing and testing the mains, services, and meters. Nothing past the regulator and into the house which is lower pressure. – decker Mar 1 at 19:21
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The fluid kids use to make bubbles is the best liquid to test a joint in a gas pipe. At $1 per bottle, it is clear when you pour it over the joint, and just like a kid blowing bubbles a leak will show anywhere on the joint.

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That is a good answer for "how do I test for leaks," but it seems to be missing a lot for what the OP actually was asking. Expand on your answer! :) – ShoeMaker Mar 24 at 23:40

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