Ask around. Ask your friends, ask your neighbors and get referrals. Nothing is more powerful than the testament of someone who has had a local plumber in their home and can speak to his/her capabilities.
If life has been hectic and you never seem to have time to collate a list of emergency services then you may turn to the Internet to help you to solve the problem. There are many plumbing services listed on the Internet. Many plumbing companies are willing to turn out not only 24/7 but 365 days a year too.
In order to summarise, the best plumbers to call out to repair your condition will be the plumbers who are able to get to you the quickest, provide you with a reasonable cost and have the expertise to carry out the job and complete it correctly. Everything else is actually not slow drain worth the work.
Leaks can come from so many sources, so you know that this is going to take time to locate and rectify. At least in this case there Trustworthy plumber is actual evidence that can be tracked. A hidden leak can drip on and on for a long time, silently adding money to your water bill.
Finding plumbers in your area does not have to be difficult. Usually they have listings for your area on the web or through other informational books that list businesses in your area. This way you may connect with a Local plumber for all your plumbing needs.
Before choosing any plumbers in your area be sure you pick a contractor that has experience with similar projects as yours. Plumbing in your area isn't the same as say New York or Chicago, unless of course you are from one of these cities. Ask for a reference or two for plumbing jobs that they have completed in the past.
When you are ready to commission the work, ask for the quote in writing and ensure the final bill is broken down. That way, there will be no room for inconsistencies between the two figures.