Hi I am looking for advice. I am remodeling kitchen in Florida and have two stubbs at different heights sticking out of concrete block wall in kitchen. When I removed a part of the cinderbock, there are two horizonal drain pipes running about 32 and 40 inches to vertical drain and vent stack? I can post pictures as I do not know if I am explaining this right. I will be installing a single kitchen sink but confused as to why two pipes? House was built in the early seventies.