• Excess hair in the drain. Typically resolved with simply removing the piled up hair and throwing it away. If the hair cannot be easily reached, plumbers have specific tools that can gather it up and unclog the drain.
• Grease. While it is a well known fact that grease solidifies once it dries, people still tend to believe that it is alright to pour down the drain, generally because it is still hot and in liquid form when they do.
• However, drains are often much cooler past the sink drain and as the grease passes through, it also clings to the sides and any other build up in the pipes. It then dries and hardens, causing a backup in the drain. Simply pouring hot water into the drain is often not the answer, though it is a common belief.
• However, since the grease merges with other particles inside the piping, the buildup typically has to be purges manually. A plumber will often have to unscrew piping and clean it or use heavier chemicals to actually clear the obstruction.
• Food bits. Just like with the grease, many times people don’t think much about letting a little bit of smaller foods go down the drain, but, also like the grease, it can merge and stick as well.

It is really important to remember that drains and piping are not completely straight, if they were then most of the time common clogs would be completely avoided, but since they curl and curve to fit, everything that goes through them has a chance to buildup in the bends.

Build-Up

Once a buildup pile begins, everything going through the drains has a chance to cling and cause the problem to get bigger. Eventually, not enough water is able to pass through the obstruction and the drain finally clogs up.