One way to find a great plumber is employ an old human skill called conversation. That is, you talk to people and ask them if they can recommend a good plumbing contractor. That is a rather old-fashioned way for me, cutting out the computer and involving communication directly with humans as it does, but it can work quite well for some people. Anybody local would work, from your neighbors to those in line at the local taco stand. You should, of course, back up these personal contacts with some research of your own. You should also consider the source, and verify if the plumbing contractor they recommend happens to be themselves, their best friend, or one of their relatives. Having established authentic and disinterested recommendations, a list of locally recommended plumbers is a good place to start your search for a qualified professional plumbing contractor.