“Don’t assume that every Mr. Fix-it advertising his services in the local Pennysaver or on Craigslist is a licensed plumber,” says one New York plumber. There is no national standard for issuing licenses. Some plumbers are licensed by the state, others by the counties they work in. Check with your local city hall or chamber of commerce. They should be able to direct you to the appropriate source for a list of licensed plumbers in your area.