Plumber vs Drain Cleaning specialists

In the past we've had a drain cleaning business come out and fix a clogged drain issue. They charged $50/hr and were done in less than an hour. I thought it was money well spent. I want to do it again, but I can't seem to find the drain cleaning specialists. How can I find a local drain cleaning specialist (as opposed to a general plumber)? Is there a special category for them that I should be looking for?

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Like Roto-rooter? They should be in the yellow pages with the rest of the plumbers who advertise. Most of these guys do general plumbing work but use drain cleaning to drive business. Whoever you use there shouldn't be that much difference in cost if they're just snaking out a drain.