We have a 2 story home with a septic tank. All piping connects into one that feeds into the tank. The kitchen sink is between the washer and the connection going to the tank. When the washing machine drains, I hear gurgling in the kitchen sink. If water is in the sink, the air will push the stopper out. This does not happen when you use any 3 of the bathrooms that are on the opposite side of the house from the washer. The washer cast iron drain pipe has been cleaned several times over the past 20 years for build up. There is no water backing up anywhere - just the gurgling sound.
I have tried the baking soda and vinegar down the kitchen sink several times. I would try doing it to the washer pipe but that's a lot of soda and vinegar! Any suggestions?