Pressure Testing an new underground gas line
Hi all,
I am in the process of adding a new coated 1/2" natural gas line underground to a patio area.
I wanted to pressure test it before I bury it and I cannot seem to find the leak. I have a gas pressure valve from Home Crapo that goes up to 15psi. I filled the pipes up with this on and cannot get it to hold @ 15 psi for more than a few hours, in about 3hours it drops about 1/2 psi or 3/4.
I have coated all the threads with a good quality gas pipe dope, (Rectorseal 5) and everything is nice and tight. After cleaning the excess dope off I coated the pipe with varying degrees of a soapy solution and I cannot see any bubbles. I have installed gas line before adding on to an existing line and have never had a problem like this. Of course I have not pressure tested before just checked with a soap solution while the gas was on.
I thought it might be the gauge so I took the 8" stub a cap and a 3/4-1/2 bushing (to adapt to the 3/4" gauge and just tested this but I still get a loss of psi. Am I under the wrong impression that this should be completely air tight? I found an old thread (Aug 2005) on this forum that said 10 psi for 15 minutes. Can someone tell me what the national code is for this and perhaps explain what I should expect to happen. I would really appreciate it. I'm going to be adding more pipe to this but wanted to test this area so I can back fill it right now. This is not going to be inspected but I want to do it right.
Sorry for the long post but I offer advice as a masonry/concrete expert on a forum and seems like I always have to ask for more info before giving an answer I can live with.
I hope this is enough info. I have another question about using a ratcheting threader but I will reserve that for later. All this pipe has factory threads.
Thank for any help