I called a plumbing company to see how much it would be for them to come out and unclog it. They quoted me a price of several hundred dollars. Of course I didn't want to pay that so I looked into other options.
One tool that is recommended is a snake auger cable which is a long metal coil that you put down the drain and rotate it to try to unclog the obstruction. I went to the hardware store and found a few different kinds to choose from. I went with a 25ft cable that had a handle and a crank to help you turn it. It cost only $15 which was not bad. They are also available online at sites like Amazon.
So I get home and give it a try. Under the sink, there was a place to open up the pipe using a wrench. Once that was off, I was able to put the cable into the pipe. This can get messy quickly so I recommend wearing gloves, having plenty of rags or paper towels, and also have something to cover the floor.
Getting the auger down the pipes can be difficult. Rotating it when you get stuck helps get the cable around corners and further down the pipe. Keep pushing it in and turning the cable as you go. Eventually it will stop. This most likely means you have hit the clog, or you just can't go any more. Pull the cable out slowly. You will probably have to rotate it the opposite direction to get it out.
Once it is out, see if there is any gunk that has been collected by the coil. If you are lucky, there should be a lot of stuff collected on the end and that means, it is working. Clean off the cable and set it aside. Close up the pipe and run the hot water. This should help clear out the left over debris and let you know if it is still clogged.
After I used the auger on the drain the first time, it was actually still clogged. I was disappointed but I decided to try it one more time just in case. This time, I put lotion on the cable to help it slide down the pipes. I think this helped because I got it further down the pipe. I kept turning it, but eventually the cable kind of twisted on itself because there was too much torque. I actually bent the cable which is not good.
I figured I better get it out before it got stuck, so I reversed it and slowly pulled it out of the pipe. It did pull out more gunk so that was a good sign. I cleaned it off and followed the same procedure of flushing it with water. This time it didn't get backed up! So the persistence and patience paid off.
If you have a clogged drain and the liquid cleaner is not working, I would recommend trying an auger before calling a plumber. It can save you a lot of money. Tips from my personal experience would be to lubricate the cable so it slides easier. Also, don't turn the cable too tight. There can be some tension, but if you do it too much, the cable twist and buckle on itself and this can bend the cable causing it to be ruined or get stuck in the pipe.
If you have tried all this and it still doesn't work, then you might have to call a plumber. Good luck unclogging your drain!