Upon arrival today the powered attic exhaust fan was venting completely clearing the attic of any heat and possible gas fumes or build up. Electronic testing followed by micro leak gel confirmed a steady stream of natural gas leakage at the threaded joint of the half inch stopcock Shut down attic supply line at the 1-in tap in the basement Replace half inch stop valve on attic Repressurize and retest with electronic All equipment is ready for full service. Power was never interrupted and thermostat settings were never changed