What was found
AIR TURN BACK. IN CRUISE O2 DROPPED TO 150 PSI. REPLACED CREW O2 BOTTLES, USED SONICAIR AND SOAP LEAK CHECK FOR ALL FLEX LINES, ON DEMAND REGULATORS, O2 BOTTLES, ALL ACCESSIBLE (B) NUT CONNECTIONS AND LINES, REG AND SHUT OFF VALVES. BLOW OUT DISC STILL INTACT. LEAK CHECKED FOR 24 HRS. TAXIED WITH CABIN PRESSURIZED.ALL CHECKS DONE WITH NO DECAY NOTED.SYSTEM MAINTAINED PRESS OF 1725 PSI.