So I'm installing a ventless NG heater in my attic. Ran 1/2" black pipe from my basement. About 25-30' of pipe altogether. Pressure tested at 15 psi, no leaks. I cut the 3/4" pipe running to my HW heater and range and tee'd into it. I added the tee, a union, and a 2' length of 1/2" pipe (hadn't hooked it up to the rest of the new pipe yet). I'm now trying to pressure test this part of the system. However, the system won't pressurize at all. The needle doesn't move off the stop of the gauge--I ran my compressor on it for more than 5 minutes. The 3/4" branches off from the meter, and a separate 1" pipe feeds the furnace. The range is off (no separate shut off), and valves to the furnace and HWH are also off. I soaped up the new joints (both when trying to pressurize, and with the gas turned on) and saw no leaks. So where the hell is my air going? All the new joints are right in front of me, and this would have to be a HUGE leak to be outpacing my compressor, right? A few more points: 1. There is SOME pressure in the system--I turn on my stove and can hear air hissing out. Still there after an hour. 2. With the gas on, the meter doesn't budge--it has a 1/2 ccm dial on it which is super sensitive. All in all, I'm pretty sure I don't have a gas leak under normal conditions. If this was water I'd call it a day at this point. I thought that maybe I had a leak that only showed up under pressure, but again, the system never pressurizes. Maybe there's a bleed down valve at the meter somewhere? So what's my next step here? I could put a valve upstream of the new joints, but downstream of the main branch point. However, it would involve threading 2 more sections of pipe, and introducing 2 new joints to the system. I bought a NG leak alarm as well... Any other thoughts?