A universal inlet adapter for a leak detection device using a pressurized detection media for detecting a leak in a fluid system, the fluid system having a fluid duct, the universal inlet adapter comprising: an inflatable bladder having opposed ends and being selectively transitional between an inflated configuration and a deflated configuration, the inflatable bladder being configured to be engagable with the fluid duct to form a fluid tight seal therebetween as the inflatable bladder transitions from the deflated configuration to the inflated configuration; a test fluid delivery tube extending through the inflatable bladder such that the inflatable bladder is disposed radially outward from the test fluid delivery tube, the test fluid delivery tube being fluidly connectable with the leak detection device for delivering the pressurized detection media into the fluid duct for testing; characterized by a pair of rigid end caps (32, 34) coupled to the inflatable bladder, each rigid end cap (32, 34) including an insertion portion (31, 33) and a flange portion (35, 37) extending radially outward from the insertion portion (31, 33), the pair of rigid end caps (32, 34) being coupled to the inflatable bladder such that the insertion portion (31, 33) of each rigid end cap (32, 34) is inserted into a respective one of the opposed ends of the inflatable bladder, each rigid end cap (32, 34) including an internally threaded aperture; and a pair of locking rings (36, 38) configured to cooperate with respective ones of the pair of rigid end caps (32, 34) to secure the bladder therebetween, each locking ring (36, 38) being configured to fit over a respective insertion portion (31, 33) of the pair of rigid end caps (32, 34) and abut a respective flange portion (35, 37) of the end caps to secure the inflatable bladder to the pair of rigid end caps (32, 34), the test fluid delivery tube being externally threaded and adapted to engage with the internally threaded aperture of each rigid end cap (32, 34); and the engagement of the pair of rigid end caps (32, 34) to the test fluid delivery tube fixing an axial length of the inlet adapter during inflation. an inflatable bladder having opposed ends and being selectively transitional between an inflated configuration and a deflated configuration, the inflatable bladder being configured to be engagable with the fluid duct to form a fluid tight seal therebetween as the inflatable bladder transitions from the deflated configuration to the inflated configuration; a test fluid delivery tube extending through the inflatable bladder such that the inflatable bladder is disposed radially outward from the test fluid delivery tube, the test fluid delivery tube being fluidly connectable with the leak detection device for delivering the pressurized detection media into the fluid duct for testing; characterized by a pair of rigid end caps (32, 34) coupled to the inflatable bladder, each rigid end cap (32, 34) including an insertion portion (31, 33) and a flange portion (35, 37) extending radially outward from the insertion portion (31, 33), the pair of rigid end caps (32, 34) being coupled to the inflatable bladder such that the insertion portion (31, 33) of each rigid end cap (32, 34) is inserted into a respective one of the opposed ends of the inflatable bladder, each rigid end cap (32, 34) including an internally threaded aperture; and a pair of locking rings (36, 38) configured to cooperate with respective ones of the pair of rigid end caps (32, 34) to secure the bladder therebetween, each locking ring (36, 38) being configured to fit over a respective insertion portion (31, 33) of the pair of rigid end caps (32, 34) and abut a respective flange portion (35, 37) of the end caps to secure the inflatable bladder to the pair of rigid end caps (32, 34), the test fluid delivery tube being externally threaded and adapted to engage with the internally threaded aperture of each rigid end cap (32, 34); and the engagement of the pair of rigid end caps (32, 34) to the test fluid delivery tube fixing an axial length of the inlet adapter during inflation.