I'm tackling a stubborn clog in a kitchen sink. I first took out the P-trap, but it was pretty clear. I then tried a 15' plumber's snake, put it in past where the p trap connects, and got the whole length into the pipe without unclogging it. I picked up a 25' snake, and it keeps buckling in the pipes, so I don't think I'm getting it in much further than the 15' snake.
Is there any trick to keeping a snake from buckling in the pipes, which prevents it from going in further? If a 15' snake didn't do the trick, is it time to call a professional?