I have added two flex-pipe gas line extensions to the existing gas piping. Everything is working properly and there are no signs of any leaks while testing for bubbles with soapy water or any smell of gas whatsoever over a week after the installation.

Now, I need to pressure test the new section for inspection. I have a 15psi test gauge which will be attached to one of the new fixtures and I will close the remaining shutoff valves at the end of each flex-pipe extension AND close the shutoff valve that was in the existing black pipe that is just before the split/manifold.

The issue is that there is a pressure regulator between that shutoff valve in the black pipe and all of the end shutoff valves.

Will I damage the pressure regulator, specifically the internal diaphragm, with ~15psi of air pressure?

Will the pressure regulator release any pressure through its vent and prevent the pressure test from succeeding?

Thank you. Eddie

Before modification

After modification

2 Answers 2


The code is not very clear and I was getting all kinds of different and vague answers from certified plumbers and even the local chief mechanical inspector. So I emailed this question to Maxitrol, the company that makes the regulator in my home, and they told me this...

"With regard to a line pressure test, NFPA 54 in Chapter 8 states that during a line pressure test gas controls including the regulator must be isolated or removed from the test."

And this...

"The outlet side of the regulator should never be exposed to an incoming gas pressure"

New configuration looks like this... Final Config

Update: 6/10/2021
I had my (first) inspection yesterday.
I heard (in a video) that shutoff valves can not be pressure tested. Based on what I heard online as well as a section of the NC code that says "New branches only need to be tested with noncorrosive leak-detecting fluid" I did NOT have my new branches pressurized with a gauge attached.

Turns out what I heard and read was wrong. The inspector told me that I needed to attach a gauge and pressurize to at least 10 lb. for 24 hours.

I tested to 15 lb and...
YES, the valves CAN and DID hold the pressure.
And YES, I passed my inspection today.

My guess is that you will be fine to pressure test the system. It would be silly if a component of the whole system had to be excluded from a pressure test and added afterwards.

What is the brand and model number of the regulator? It would be trivial to find a spec sheet online or call the manufacturer.

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