The Sink Drain Set-up
For many people, the sink drain is just a hole in the bottom of the sink that the water goes down. But there is a little more to it than that. Under the strainer body that you can see in the sink is a rubber gasket and a locknut. These connect to the strainer sleeve which connects to a tailpiece. All this leads up to the trap. The trap is where things that aren't supposed to go down a drain go when they fall in. The trap has a clean out plug on the bottom and then winds back up and connects to the pipe that takes the water out to the septic or sewer.
The trap is a U-shaped pipe that keeps water and waste from washing back up into the sink. Of course if you have a clogged pipe and you keep running the water, your sink can still overflow. At the bottom of the trap is a clean out plug. This can be unscrewed to get out grease, hair or other things that may be clogging up the trap. If you drop something down the sink that is small, you may be able to get it out. If it is big, you may have to take off the entire trap. Always make sure to put a bucket under the pipe if you are unscrewing the clean out plug or removing the trap.
Prevention and Clearing Clogs
The best way to keep a drain free from clogs is to use a strainer. This will keep most things from going down the drain. Don't pour grease down the drain ever. Grease not only hardens when it gets cold but it sticks to the sides of the pipes and catches other things that come by. Eventually you will have a clog. If you do drop something in the drain, go and get it. Don't assume it won't do any harm. It can catch other things that make their way down such as hair, soap scum or other debris and cause a problem later.
You can clear out a clog by trying to use a chemical drain cleaner. There are many to choose from that work on clogs where no water is present or where there is standing water. Follow the manufacturer's suggestions. However, sometimes you will need to do it more than once. If that doesn't work, use a plumbers snake. This will go through grease and hair and pull it back out. If you aren't making any progress, then your best bet is to call a plumber. A plumber has special equipment that can get to places that you cannot.