Why does my kitchen sink fill with water when my washer drains
I have a single story home built in 1961, and recently my kitchen sink drains slowly and when I run my washer which is in my garage, the water from the washer draining fills the kitchen sink. I have tried rodding out and running water down the vents for the washer and kitchen sink, with no joy. All other drains in both bathrooms run normally, and I looked in the clean out port in the main line outside and the main line is draining normally.
Any thoughts?
Thanks
Chuck E.