Here in Alabama a plumber working for another company is not licensed ,he is certified. We have a state wide certification system .
To be a plumber you are given, yep given an apprentist card. Then the work and study starts, to get the journeyman you have to pass a test { non union no time limit .same test) Then the masters, its also a test!! a smart guy can slip thru the system in a few years if he or she can pass the tests. Now the license, you have to have your masters card in plumbing and gas (if you want to put in water heaters){also bonds and insurance} to buy a LICENSE to work. the catch is every small town, county and most any place that is incorporated can get you for a license .in my 3 county area we once counted over 90 licenses just to be legal.Most of the small one man band shops get their masters in plumbing and gas, get the state certification card, then a license for their home county and biggest towns in their work areas and when they get caught in a small area that they are not licensed they PAY THE PIPER!
! As most of you guys know ,we live in a RIP OFF state no one could really be legal to run a state wide business without a (wheew) whole hell of a stack of licenses. However if you have a JM or Master {certification) card you can work anywhere in the state for the other guy. To get a license to JUST clean drains its the same as selling peanuts just a vendors license go figure!! I retired my gas and master plumber card in 2010 but to go back to work I simply pay 1 yrs dues and go for it but it aint happening Im done