I've been having a helluva time with the gas line in my shop. The old shop had a gas line from the meter at the house, underground into the shop attic, then to the heater in the shop with no gas shutoff. The guy who put the line in didn't install one at the meter. So I took the line apart where it enters the shop, installed a union and a shutoff valve. I took the elbow off where the line goes down to the heater and added a tee, and extended the line to the heater into the new shop with a few 10-foot sections of pipe and couplings, then installed all the fittings and pipe to get to the heater.
I needed to pressure test it and it has to hold 10 psi for 24 hours. It didn't. I figured it was probably the union I installed, so I tightened it a bit more. Still leaked down.
I climbed up into the attic to see if I could find the leak with some soap. Nothing where I looked.
So I decided to take off the union I installed where the line enters the shop and cap the line, just in case the problem was still the union. In doing that, I noticed the pipe coming out of the wall seemed a little loose. It shouldn't have been, because it should have gone straight to an elbow, then up into the attic. So I climbed up into the attic and removed the horizontal line. To do that I had to disassemble everything in the new shop....for the 4th time. Then I tried to tighten the vertical section. It just turned and turned, and never got tight. So I decided the elbow at the bottom was either broken, or something weird was going on. But I was now sure that was where the leak was since the nipple going into the shop was a little "floppy".
I cut a hole in the drywall near the floor inside the old shop, and I found out that for some STUPID reason I installed a union there 11 years ago. The 10-foot pipe wasn't long enough to get all the way into the attic back then, so I added a short piece at the bottom. Why I didn't use a pipe coupling I'll never know...must not have been thinking clearly. LOL!
Anyhow, I replaced the union with a coupling, and re-assembed the pipe all the way into the new shop. I was sure I had fixed the leak now, since the union had gotten loose somehow. So I re-assembled everything. It still leaked down.
So this morning I pressurized it with 30 psi to see what would happen. It dropped before too long. I climbed up into the attic again, and used soap to check the fittings. I found a small leak at a coupling I installed 11 years ago. So I tightened it. That loosened up the joint at the tee that I installed. Now I have to disassemble everything in the new shop again so I can tighten that fitting without loosening everything else.
I have put a lot of pipe dope on these threads. I cranked down on the pipe pretty hard. You would think it wouldn't be this hard to hold 10 psi. What a PITA...and I'm still not finished.
But I did get the vent done after disassembling it 3 times too.