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After installing some new CSST with black iron end points and pressure testing at 5 PSI, is it bad to lose 1/10 of a PSI (0.1 PSI) in 24 hours?

I cannot identify any leaky joints with solution and I've seen claims that 1 PSI in an hour is an incredibly tiny leak so could a tenth PSI drop be just an error in temperature change?

FWIW, the old gas line is still in use and I'm prepping for a weekend cutover from the old to the new lines.

isherwood
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MonkeyZeus
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    I'm not a pro, but it seems like that could be attributed to a temperature swing. – isherwood Sep 25 '20 at 17:58
  • @isherwood It pains me to ask and I think I know the answer but if 0.1 PSI is lost every 24 hours for several days then is that more telling of a leak? – MonkeyZeus Sep 25 '20 at 18:06
  • If the ambient temperature is stable and the pressure keeps dropping indefinitely, I suppose so. – isherwood Sep 25 '20 at 18:09
  • I think this older thread about gas line testing will be very helpful. Check with your local building inspector and your CSST manufacturer about the correct test pressure in your area. https://diy.stackexchange.com/questions/24835/how-do-i-pressure-test-a-natural-gas-line-and-what-do-the-valve-pressure-ratings Home Flex, a maker of CSST, also sells a 15 PSI pressure test gauge. – Jeff Wheeler Sep 25 '20 at 18:20
  • @JeffWheeler Thanks for the link. I am using the HOME-FLEX 15 PSI gauge. From my research I understand that you're not supposed to test at the gauge's full capacity and at minimum you should do double the gas's PSI or 20% of the gauge's capacity, whichever is higher. – MonkeyZeus Sep 25 '20 at 18:29
  • I want to say our test is at 30 psi and if they see a change in the 10-15 minutes they are inspecting it will fail, .1 is small but at only 5psi test pressure may not be a problem in open air but what if in a wall? Then the gas could build up. If testing at a higher pressure I would not be worried but so close to actual pressure compared to what I am used to testing at would give me concern. – Ed Beal Sep 25 '20 at 18:52
  • A leak of 0.1 psig is small ;But 5 psig is low pressure. I would leave pressure in it a few days to determine if it was caused by temperature change. – blacksmith37 Sep 25 '20 at 19:03
  • @EdBeal 30 PSI concerns me after watching https://www.youtube.com/watch?v=akysJBsfF2M and then https://www.youtube.com/watch?v=fPYyDG9an-c. Looks at the comments on the second video. I prefer not to create issues by breaking seals in my valves. – MonkeyZeus Sep 25 '20 at 19:09
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    @EdBeal Additionally, natural gas runs between 1/4 - 1/2 PSI so a 5 PSI test is 10-20x operating pressure. – MonkeyZeus Sep 25 '20 at 19:18
  • It depends on the service 2 psi is usually commercial but people with gas swimming pools may have 2 psi systems and commercial usually do at least in my area , homes are usually 3/4 psi in my area. I am glad you watch u-tube videos I have installed quite a few systems in homes and remodels ,,, keep on watching uTube , go try to make glow sticks my son wasted a bunch of $ trying to get that scam to work, or eat some tide pods I see it on u tube! But don’t take that as an absolute answer. As I said my county uses 25/30 it has been a few years since my last install, a change at 5 psi is a leak – Ed Beal Sep 25 '20 at 20:00
  • @EdBeal I'm sorry that YouTube has caused such distress in your household due to glow sticks; I will try to refrain from eating Tide Pods. Not sure what you think of me but I am not some fly-by-night hack-job guy that says "it's good enough". This project has taken me about 1 month and I've been talking with people in the trades, reading guides, forums, and watching countless YouTube videos while taking care of business on the porcelain throne. I share this home with my family so I'm sorry for offending you by wanting to get insight from experienced people. – MonkeyZeus Sep 29 '20 at 12:06
  • That’s funny uTube has caused me no distress I was simply pointing out there is a massive amount of bad information out there and anyone that takes that info as “truth” without question is in for problems. – Ed Beal Sep 29 '20 at 13:48

2 Answers2

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Home Flex's CSST manual http://homeflex.com/downloads/HOME-FLEX_Installation_Manual.pdf tells you to test at 150% of the product's operating pressure. A good rule of thumb is always check the product manual first.

When people say 20% of a gauge's capacity, they don't mean over-pressure the gas pipe system; they actually mean get a different gauge if you need to. Don't, for example, use a 90 PSI gauge to test a 3 PSI gas system; it's not designed to be sufficiently accurate for the test. The reason people say test at minimum 20% on the gauge is the NFPA 54 fuel gas code §8.1.4.1 says shall have a range such that the highest end of the scale is not greater than 5 times the test pressure. In any event, I believe you have the correct gauge for your project.

Regarding the test duration, your local building official is the authority on this; but NFPA says for a residence the test duration shall be a minimum of 10 minutes. The duration of the test shall not be required to exceed 24 hours. It further says Any reduction of test pressures as indicated by pressure gauges shall be deemed to indicate the presence of a leak. Sucks, right? The better your equipment and the more diligent you are, the more likely you chase a ghost, because the code is non-specific.

That's why I'm suggesting ask your building inspector. He or she will probably tell a story about some local system they can't believe never exploded, and tell you the 0.1 PSI is okay. Nobody here wants to be the one to say that! :D

Jeff Wheeler
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    I agree Jeff but different counties have different tests as I mentioned ours uses 25 or 30 And the inspector marks the gauge when he goes in and checks it after verifying shut offs venting and fresh air supplies meet minimum code takes all of 10-15 minutes, any change and it won’t get the green sticker allowing the gas company to set a tank or connect natural gas. – Ed Beal Sep 25 '20 at 19:58
  • I have heard that testing of a whole system of *new installed* black steel gas pipe systems was done at up to 30 psi with compressed air to actually cause leaks to occur in defective fittings or pipe. Testing of CSST would not be at anywhere near such pressures. – Jim Stewart May 13 '21 at 21:24
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TL;DR

Use a manometer and get on with your life.

After switching to the new gas lines and losing some sleep over this issue I finally decided to be okay with the situation for the fact that I used to get whiffs of gas/mercaptan with the old system but my new system has no trace of smell.

Eventually my friend came over with his manometer and we properly tested my gas lines and found no leaks.

MonkeyZeus
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