gas line test – acceptable pressure drop
Installed the gas system (for low pressure – 1/2 lb gas service). Pressurized to minimum of 10 lbs pressure. System holds pressure with no acceptable drop for the required 15 minutes, but loses pressure at about 1lb/hour. Is it standard practice for professional installers to search for leaks in a case like this and tighten the system until it holds the test pressure indefinitely?
Thanks
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Replies
IIRC inpectors here wath the pressure go in then tag it with a date and time and come back in 24 hours to check pressure.
Not sure what is acceptable.
Sounds like you've got a leak.
[email protected]
Around here.... inspectors look at guage when they show up, walk the job and check the pressure when they leave. This will likely pass the inspection..... but safety first!
Agree on the leak assessment. Been looking for them with 15 lbs in system and the specialized glow in the dark leak detector. Haven't found anything immediately obvious, but not entirely pleased with the specialized leak detector....tends to have tiny bubbles out of the container which take a long time to dissipate when the fluid runs around the fittings. May try dish detergent. Any other inspired suggestions?
Thanks
Call the gas company and report a leak. They'll bring some specialized sniffers and track down the leak.
You might get charged for it, or maybe not.
Understand that I have no clue as to if this is a good idea or not. I know nothing about plumbing but my wife is paranoid about gas leaks and everytime she calls, they come running.
jimfka (formerly known as) blue
He doesn't have any gas in the system.
I would pump it up to 100 PSI and use windex on every joint until I found the bubbles. Where I am working we have a test on the radiant tubing and another test on the underslab water lines. Gauges on both that I look at almost every day, and no drop in two months.
agree zero pressure drop should be standard. Interestinglyu enough the licensed HVAC contractor turned system over meeting the 10# for 15 minutes criteria, but certaintly not meeting the no pressure drop criteria. found leaks. tightened. holding 15# for five + days.
Are you testing against valves or are the valves open & capped on the other side?
“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.” —George Washington
Valves are open and capped on down stream side. Appliances and flex lines are out of the system.
Another question..... you prefer the specialized gas leak detector or dish detergent for chasing leaks?
Thanks
I do large new instalations, snoop¯ & other brands tend to be a bit spendy, so we use use dish detergent & a lot of it ;-)
If the gauge can handle it pump it to the max--- that helps find leaks a bit faster.
Common place for small leaks is the packing bonnet on the valves.
“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.” —George Washington
Up here in Canada it is 15 pounds for a minimum of 15 minutes. You probably mean you have a 1/4 pound system so pumping a system up to 15 pounds means it being tested at 60 times normal operating pressure.
That's good enough for me. If the powers to be wanted an indefinite period of time without leaks, like refrigeration, they would have demanded it. Nowhere in the code does it say anything about being leak free.
I used to leave the guage on while I cleaned up or painted the lines which was longer than 15 minutes but on the tag I always put 15 pounds for 15 minutes. I was actually one of the few guys in our team that even had a guage and used it all the time. Some guys used guages that were wrong (code specifies size) and wouldn't read a small leak in 15 hours let alone 15 minutes. Maybe your guage is also the wrong guage.
You have to remember that natural gas, or propane for that matter needs a specific ratio of oxygen and gas to be combustible and the range is very small. Pretty safe in fact though my wife doesn't agree with the physics. So what I'm saying is that you could have a small leak of gas and never reach the oxygen/gas ratio to ever explode. I'm sure when "they" wrote the Canadian Gas Code this was all factored in.
So, if the local inspector wants 24 hours and it's okay for 24 hours what happens if you leave the guage on for 48 hours and find a leak? Would you accept that? What would you accept?
Now I have a pet peave with inspectors of anything when they try to make rules as they seem fit and are not covered by regulations. If a local district decides it wants a 24 watch on gas line guages then make a local ammendment and send copies to all concerned. I accept that and applaud it but my hackles rise when I hear the local inspector say "I want such and such". If it is as good as he says it it is, he should write it down and it becomes a"local jurisdiction issue" and not a whim.
In a former life I was told I could only enforce the law, not make them up as I go.
roger
Edited 10/21/2007 12:24 am ET by roger g
Edited 10/21/2007 12:25 am ET by roger g
Around here, the line is expected to hold pressure overnight. That is, the line is pressurized, inspection is called for, and the inspector comes the next day. This can be a challenge, as our typical 30-40 degree daily temperature swing can influence the test, even without a leak! Off the top, I would say you have a leak. Find it and fix it. OR- look at it this way: We don't test to please the inspector. We test to check our work. The inspector is only there as a fall-back. Fooling the inspector will not fix the problem.
Edited 10/21/2007 12:09 pm ET by renosteinke
I think you must be talking to someone else. I don't try to fool any inspectors. I used to inspect.
roger
Sorry, Roger ... my comments were not aimed at anyone personally ... I guess I forgot to click "all" .... drat that software! I was responding, though, to the implied way to finesse the test: pump it up just before the inspector arrives ... then hope he leaves before the drop can be noticed!
No problem. I find that the gauges most people use to check pressure is wayyyyyyyyyyyyyyyyyy too small and is capable of higher pressure. Off the top of my head our gauges must be something like 3 inches in diameter and I believe register only up to 30 psi. With this type of gauge you can see if you are loosing an ounce of pressure or something very near that so in 15 minutes or so you will notice on the gauge whether you have a small leak. Gauges which are small and are rated a much higher psi will not register a leak until you have leaked alot. I've tried several gauges on a system which leaked just for study purposes and found all what I have mentioned above to be true.
So in effect, if you use the wrong gauge, keep it hooked up a long time.
By pumping a system up to 100 psi to find a stubborn leak you must first remove the 30 psi gauge and the check to see if the valves are capable of taking that pressure. Most won't and you will find leakes that weren't there before in fact you might have created them. With a stubborn leak try ramping up the pressure and keep testing. Once I had a leak which I thought was buried behind a wall so I cranked up the compressor to about 130psi until I heard the hissing behind the wall.
roger
I have tested black pipe gas lines to 100 PSI and they easily hold it. That's without any valves or appliances connected. The procedure I have always used and seen others use is to rough in the gas lines and test them as above. Around here the propane company will come out and do a low-pressure test after the valves, flex connectors, and appliances are installed.
I've seen alot of people do alot of different things and think it right. What is right is what is written in the code. Remember, if the powers to-be wanted 100psi, it would be written, wouldn't it. Granted they might give a minimum pressure test pressure required but at 100psi on propane that is 200 times operating pressure. A little extreme, I would think. We don't test anything in building whether it's plumbing, electrical, trusses, beams etc etc 200 times fudge factor. Because alot of gas fitters are plumbers (I'm not) they are used to pressure testing plumbing up to 100 psi(nice round figure) which is only about twice operating pressure. Even boiler systems run at a minimum of 12 psi so at 100 psi is 8 times operating pressure. 200 times doesn't make a whole lot of sense does it.
Sure if it makes people feel warm and fuzzy testing pressure lines at 100psi, that's fine but code it aint(at least any code I've seen). I would ask whoever is testing the piping about what the code says. It should be something he knows instantly and not something he "has to look up". If a person doesn't know that I would be suspect at other stuff they don't know. Not that a person has to know everything by heart but they should that one.:)
With natural gas, after evrything is hooked up, we would turn on the gas and without anything on we would do what is called a dial test. We would mark one of the meter dials (the main gas meter) and wait about 30 minutes to see if it moved.
With propane we never had a meter to do a dial test so we just soaped up and checked all connections.Just like the installer might have done when they pressure tested the system and were looking for a leak. I guess if your guys are doing a low pressure test I would think they would be disconnecting from the tank and hook up a pressure meter and pump it up to 1/2 psi and watch. Much more than that they run the risk of rupturing the diaphrams in all the gas valves.
I've seen guys pressure test systems at a high pressure and they think by shutting off the shut off valves would do but found the valve had in fact leaked and destroyed the gas valve in the appliance.The appliance valve/reg is only designed for a certain incoming pressure.
For example in natural gas the operating pressure in the lines is supposed to be about 7 inches of water column (1/4 pound) and that is what's going into the appliance but that pressure is regulated down again to 3.5 inches of water column which is what comes out to make the flame. ( Damn, I haven't thought about this stuff in years. I hope I'm right:) )
roger
B149 has changed.
for gas pressure up and including 2psi 15# for 15 min or 15# for 60 min if length of pipe is over 200'
for gas pressure over 2 psi up to 33 psi 50 # for 60 min or 50 # for 180 min if length of pipe is over 200'
for gas pressure over 33 psi 1.5 times the max operating pressure for 180 min.
all welded pipe is the greater of 50 psi or 1.5 times max for 180 min.
Min diameter of gauge is supposed to be 3" and the range shall exceed the the test pressure by at least 15% but not more than 300% and the increments shall be either 2 psi or 2% of the mas dial reading, whichever is less.
B149 is Canadian code.
Note (1) says pressures and times are minimum requirements, Circumstances can require more.
I know it's always changing but at a glance that part hasn't changed. Even the part about the test pressure being the minimum and circumstances could require higher test pressures. What circumstances? Not that I'm adverse to a higher test pressure but off the top of my head I can't think of a circumstance other than trying to find a pesky leak. Once found and fixed the test pressure should be back to 15 pounds 15 minutes or close to that. I would pump it up and wherever the needle stopped whether at 15 or 22 pounds I would mark the gauge. My gauge was quite big with many increments so I knew quickly if I had a leak.
What I would try to impress on newby's was to know the code and if you wanted to vary from that it was up to them but KNOW THE CODE!!!!
I wonder how many gasfitters even have a code let alone always carry it with them? I was always looking things up.
roger
roger
We just had a meter install refused because the gauge pressure was less than 15#.
It sat overnight and the temps dropped. So now, 25+.
Just for curiosity, where are you in Canada? I've done gas fitting in 3 provinces and I've never had to leave a test gauge on a piping for an inspector to see. I'm the one with the licence. I'm the one that did the job. I'm the one who pressure tests it. I'm the one who is responsible.
I have heard, though never seen, where a gas inspector has arrived on scene ( extremely rare) and asked the fitter to pressure test the system because that particular fitter has been noted on their file for having leaks.
Maybe where you are it is like that or maybe things have changed more to be like what I hear plumbing inspections are.
roger
Moose Jaw. It's a provincial thing. We have to put a tag on the gas line showing date, type of test and sign it. Then the utility checks the test and signs the tag. No tag, no meter.
Keeps everyone honest.
We also have a red tag program where the utility or contractor can tag and shut down a system for a dangerous situation.
The only thing I see different from Ontario is that you leave the gauge on for the inspector. Which in my mind defeats the 15 pound 15 minute thing. When we did inspections we were never really sure when we would get to a site so a gauge could be on for days. If the gauge had dropped in 2 days but hadn't dropped in 15 minutes, 15 hours or 36 hours it should still pass code.
Here in BC (Island) they don't tag anymore or at least it was a on-a-again off-again thing. Very rarely do installs ever get inspected by an inspector of any kind and the gas fitting shows it. I believe the Gas Board is trying to rectify that situation but has a very long way to go.
roger
My experience shows that if the gauge goes down to around five lbs., then the shut off valve is leaking. If the gauge goes down to zero, someone over-tighten the fitting and split it.
If I remember correctly we aren't allowed to pressure test a system with any valves on. We do it sometimes but I seem to think we are not supposed to.
I have leaks from everything including someone used a hacksaw to sabotage my job or a leak inside my own pressure dial. and THAT was a pain to find.
roger
Moose Jaw eh
My sister & B I L live in Saskatoon.
“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.” —George Washington
> I have tested black pipe gas lines to 100 PSI and they easily hold it.
Same here. If the system is right, it'll hold just fine overnight. It's done with caps where the appliances will go, and the caps just stay there until after drywall and paint. Caps are easier for the other trades to work around, and they don't eff up the valves.
100 psi is nearly 7 times the code minimum and 200 times the working pressure, mainly because the working pressure is so extremely low. It would be damn difficult to work with some sort of tubing system that would hold 15 psi, but rupture at 20 - 30. Black pipe is massive overkill for gas systems because there's no economic advantage to developing a lighter duty system.
-- J.S.
When testing gas our inspectors want a pressure gauge that's double the test pressure.
Standard low pressure system ( 6 to 12" on the water column) we test @ 15 psi with a 30lb gauge.
2 to 5 pound systems we test @ 60psi using a 120 pound gauge.
40 to 80 pound systems we test @ 150 psi using a 300 pound gauge.
Having said that I have used a 100 pound gauge on a low pressure system, the inspector wanted the system tested at 50psi cause of the gauge.
“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.” —George Washington
That seems to be roughly what our code says also. Not sure about the high operating pressures above 5 pounds though. As I said before if you use a gauge like a 100 psi one, the increments are 5 pound increments or 2 pound at best.. How could you possibly tell if you lost 1 or 2 ounces in 15 minutes or an hour? You would have a leak and wouldn't know it? A 30 psi gauge might have the same number of increments as a 100psi gauge but might be 1/4 pound increments or less so a leak would be much easier detected. Also a big dial, as per our code, also makes any leak more easily detectable.
What does your code say about pressure testing and gauges? The code, not what the inspector wants.
roger
Code states for low pressure system to be not less than 10 psi, gauge to be in 1/10 increments.
“The Hand of providence has been so conspicuous in all this, that he must be worse than an infidel that lacks faith, and more than wicked, that has not gratitude enough to acknowledge his obligations.” —George Washington
(IRC) R104.1 allows the building official and their designees to expand on the definition of the code's requirements. They just can't wave or reduce the written interpretation. Then local legislators can also muck it up more. WA state says they can't change the state's interpretation unless they are Seattle or can show unusual circumstances. One city (Redmond) used the last one to enforce residential fire sprinklers - their unusual circumstance: because their fire department was so bad at responding! Know your local querks (laws, codes and officials)!
....gas line test - acceptable pressure drop.... NONE!
my thought also. Once I found the gas leak detector that I liked.... liquid ... and found the nice big bubbles and twisted a few fittings tighter...things are good as evienced by holding 15# for five+ days
I use Palmolive, great suds, in the winter I mix with windshield fluid, keeps it from freezing on the pipe. I also use a brush, not a spray. Have a good one.
A test for gas leaks would only confirm the integrity of the installation. I would say.
I wonder what an acceptable drop after 12 years is.
not having blown up?!