Gas line slow leak detection

[House Flipper]

I have installed a csst gas line that has a SLOW leak. I've tried soapy water and a product from Home depot to detect air pressure test leak. I've put 15 lbs of pressure to help detect but no luck. Been through every connection about 10 times. Loose about 1/2 lbd over night. Any tricks or tips on how to find a slow leak?
Also what is the typical pressure the gas company puts out? What do they want to see at the test and for how long?

 

[House Flipper]

...not custom, csst.

 

[ShaunCorbs]

Are you testing just the csst or a whole installation ?

 

[House Flipper]

Whole install. That was going to be my next move. Take everything off except the csst

 

[ShaunCorbs]

Need to split it into sections

Is it copper pipe ? Cap / plug leaking

All new or just the csst that’s new ?

 

[House Flipper]

Need to split it into sections

Is it copper pipe ? Cap / plug leaking

All new or just the csst that’s new ?

yep I have purchased a second pressure valve and split the line in 2 where I had a T for a later project. we are waiting now to see which side fails. Used an old black pipe to terminate and new on the other end. have taken it all apart and resealed everything. I may have found it, when I removed the T fitting I noticed the cut end on the csst was a bit rough, so i re-cut and re installed the fitting. I'll let you know how it goes.
thanks for the input

 

[ShaunCorbs]

Ideally you want to cut it using tube cutter with a csst cutting blade and not a hacksaw / grinder

Also don’t solder / use flux anywhere near it as it will eat through it like a hot knife through butter in a year or two