 After achieving this license, the journeyman plumber must work full-time for at least an additional six months before qualifying to test for the master license. And to maintain either license, the plumber must attend yearly educational seminars. If you have a plumbing or heating problem, call the licensed professionals at Bowe Plumbing and Heating Corp., owned and operated by the Ives family for over 50 years. Master license number 478C.