Rebuild of the kitchen sink plumbing was required when we decided to remove our garbage disposal. Replaced all the sch 40 PVC. I brought both sink drains to a T then down to a P trap and out the cabnet to where grey water normally goes. Before replacing we did not have problems with soap backing up in the unused sink. We use the same amount to wash hands and dishes with. Any ideas or tricks - our friends at home depot and lowes are clueless as is the facilities plumber at my work. Thanks.