Pipe Connections

• Double sinks only have one drainpipe feeding into the wall, like single sinks. If you look at the underside of a double sink setup, you will see that one sink connects to the drainpipe of the other via a long, horizontal pipe that runs between the two. Drainpipes will rely on water pressure and gravity to move debris along, meaning that long horizontal pipe will accumulate more debris since it does take advantage of gravity. Some installers may position the pipe so it slopes down to the connection with the drainpipe from the other sink, helping to avoid frequent clogs.
  
  

Plunging

• Plungers help dislodge clogs in a sink's drain by applying additional pressure to the pipe and in turn the clog. Plungers may not always dislodge a clog, but the likelihood your plunging efforts will be successful is increased by your using the plunger correctly. For a plunger to work well, the sink's drain must have at least 2 inches of standing water when you use the plunger. You must also create a tight seal with the plunger's cup around the sink's drain opening. With double sinks, you must stuff a rag in the other sink's drain, since the plumbing is connected, as well as the overflow openings in both sinks if any are present.
  
  

Kitchen Sinks

• With kitchen double sinks, a clog may occur whether you have a garbage disposal or not. Certain types of food debris will more readily produce clogs, such as carrot or potato peels or large pieces of meat. If the disposal sits on the side of the sink that does not directly connect to the wall's drain pipe, the debris that is not chopped up by the disposal will create clogs in the vertical connector pipe. When such a clog occurs, the solution may be to take apart the pipes and extract the clog. Some clogs may be severe enough to require a new pipe.
  
  

Other Techniques

• Other than extra steps for plunging and the higher chance of the connector pipe clogging, removing a clog in a double sink requires the same methods you use with a single sink that is clogged. Some clogs in bathroom sinks exist just below the sink's stopper, so removing and cleaning the stopper will help eliminate the clog. You can also use needle-nose pliers or a metal clothes hanger to extract clogs that sit just below the stopper. Ultimately, you may need to take apart the pipes under the sink and feed a drain snake down the pipe in the wall.