Our home is about 20 years old. It has 2 bathrooms. The toilets are exactly over each other (1 on 1st floor and 1 on 2nd floor) When the upstairs toilet is flushed it cause the downstairs toilet to blow air bubbles. I have tried snaking the drains in the house and have had a "re-vent" put on the upstairs vanity. Any suggestions on how to stop this. The problem did not always happen, but developed over the years we have lived here. Also the downstairs toilet "bubbles" when the washing machine drains...???? Any ideas???
FYI We are out in the country on a septic system?

 

Partially plugged sewer.
-plumber john

 

I agree with plumber john. What's happening is that when the upstairs toilet is flushed, it is compressing the air in the drain pipe because it is partially plugged. This compressed air finds its way out the lower toilet. Besides being annoying, these bubbles might not smell so good.