What is the trick to getting the snake to go past bends in the pipe? Is it just the difference between having a power snake and a manual snake? And if it is a power thing, will the snakes that attach to a drill work?

We are taking off the trap and going in under the sink but can't get the snake to go any further into the pipe than where it turns downward in the wall. What are we doing wrong? We've had the drain cleaning guy out every few years so we know it can be done.

Thanks!