Water backing up into the garbage disposal and then the sink is generally caused by food that is left in the disposal. If you leave food particles in the disposal and then forget about them without grinding them up and then sending them through the drain pipes with a good amount of cold water, these food particles will clog up your drainage system. Since the dishwasher and the garbage disposal share the same drainage pipes,you will have plumbing problems in the kitchen if you do not make sure that food particles from the disposal are cleared before using the dishwasher.
When it is time to run the dishwasher, many people are tired after work and having dinner. They want to scrape the plates and put the food particles down the garbage disposal. After that, they want to load the dishwasher, turn it on and then forget about it. However, the best thing to do before running the dishwasher is to check the garbage disposer. This is especially important if you have other family members like children helping out with the dishes. This is because children don't realize that the only food particles that should be going through the disposal should be very small. Remember, everything that goes through the garbage disposal also has to go through the same drainage pipes that you share with your dishwasher.
Before using the dishwasher make sure that you check the disposal for food particles, and as an extra measure, run cold water through the disposer and turn it on to get rid of any food particles that may be left there. This is especially important if you live in a household with more than one person living there. This is because one of the worst things for a garbage disposal is people who put things down the garbage disposal, thinking that it can liquefy anything.