I am new to the forum. I am plumbing a gas line in black iron and have the system under 15 psi test pressure. The run consists of about 18 ft of 1 inch with an 8 ft branch of 1/2". The system has lost just under 1/2 psi over a 48 hour period. If anyone has suggestions for detecting a leak of that size, I would appreciate it. Thank you.