I have a new garbage disposal. When it runs, water comes up in the other sink. I have looked at your websites and read your book, but have not found the answer.
In some cases, a disposal will be installed with a “T” to the tail piece of the adjacent sink (see illustration). With this installation, water can be pushed up into the adjacent sink. You can buy a special “T” for this connection to direct the water down, but it’s still a questionable installation.