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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 '13 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 '13 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 '13 at 22:27
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I understand your concern. But at the same time, you still need to test the whole system. My water heater manual says: "The appliance and its gas connection must be leak tested before placing the appliance in operation. It shall be isolated from the gas supply piping system by closing its individual manual Shut-off valve during any pressure testing of the gas supply piping system at test pressures equal to or less than 1/2 pound per square inch (3.5 kPa)." –  Philip Ngai Feb 1 '13 at 4:39
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But, I'm required to test at >=3 PSI. So, I can't just use the manual shutoff to isolate it. What I ended up doing is to disconnect it, and cap off the CSST line, and then use a leak-test bubble solution to verify the connections that were not pressure tested. –  Pigrew Feb 1 '13 at 16:54
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4 Answers 4

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 '13 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 '13 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 '13 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. –  fungku Mar 1 '13 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 '13 at 23:40
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The standard pressure test for new natural gas or propane pipe in my area (NW Oregon) is something anyone can do. Same for installing the gas line. (Why are there so many naysayers on a DIY forum? This is not rocket science:   Just a few new skills to learn.)

Before installing the gas pipe, I consulted with a pro (paid $80 for an hour of onsite questions). He had some good tidbits and some not so great. The best bit of advice was that to prevent leaks, make every connection with no more than two or three threads showing. Since there were 105 connections, this was a heavy duty workout over several days. Using yellow Teflon tape makes turning much easier—as does a 16 inch pipe wrench. The joint's seal is formed by the pipe and fitting being forced together and then settling (which takes hours to days). By turning until only 1 to 2 threads (out of 10) remain revealed, there was no leakage.

(The worst bit of "pro" advice was that he would have routed the pipe through the garage in the most obnoxious way. It would have been convenient to install, but a royal pain in the ass to live with afterwards. Instead, we opted to bore two holes through the garage foundation into the crawlspace and kept 98% of the pipe neatly out of the way.)

To leak test, obtain a $10 gauge as pictured (for black pipe) and install it somewhere on the pipe. In my case, I put it at the top of the riser pipe for the range. I explicitly ran 3/4 inch all the way to the range to suit the gauge, which has a nice benefit of smooth generous flow even when all the burners and ovens are on. (Total extra cost was less than $20 over 1/2 inch pipe, and no perceptible increase in hassle.)

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Since every appliance has an independent cut off valve, I closed all those and the gas meter shutoff valve, used a bicycle tire pump to pressurize the system to 30 psi and waited. If the whole system does not hold pressure for hours and hours, there is a leak somewhere. At the end, the worst leak offender was the test gauge itself. I had to clean the needle valve and use gobs of Teflon tape to get it down to reasonable levels—on the tire valve thread into the tester body, on the gauge stem's thread into the body, and a great deal of tape for the gas pipe going into the tester. For preliminary tests I tried temporary caps at the appliance feeders and those were exceedingly leaky—the pipe caps don't seem to fit tapered pipe because they lacked enough thread depth. The valves on the appliance flex hoses didn't leak at all.

Once I was satisfied that 30 psi didn't leak significantly, taking five days to drop to 22 psi (demonstrably through the test gauge), I called for inspection. The mechanical inspector walked in, saw 22 psi and said "you pass" without looking at another thing. According to the test standards (see 406.4), it has to hold pressure for 10 minutes with no perceptible drop and he had no idea if I pumped it up just as he arrived or hours before. So much for inspection insuring safety.

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?

Yes.

Should the other shutoff valves rated at 1/2 or 5 be able to withstand the 4 PSI of the pressure test?

Yes.

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.

Why not be thorough? If there is a leak at 4 PSI, it will be very difficult to assess. Run the test at the maximum test gauge reading.

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.

That is standard residential delivery, same as mine.

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"Why are there so many naysayers on a DIY forum?" - because a) in some countries it's illegal for unqualified people to work on gas. b) houses demolished by gas explosions get more press than electrocutions. –  RedGrittyBrick Dec 20 '13 at 11:35
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