There's 2 ways to go about this.

1. Buying a cleaning product - I'd recommend Formula 420. It works great, and is pretty cheap ($4.20)

2. Home remedies - easiest way would be to get a jar/plastic bag, and pour some rubbing alcohol into it. Enough to halfway submerge the pipe horizontally. Periodically rotate the pipe to hit all the interior area. Remove when clean to your desire, might take a few hours max.

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