[hydroguy]

Over the last year or so, a vent problem has been getting worst. When the washing machine is emptying the water down the drain, there does not seem to be enough venting for it. Air and water bubble up in the toilets and it sucks the water out of the toilet bowls as the water leaves the washer. I thought that maybe the vent stack was blocked, but nothing is in it.
What could be causing the lack of venting in this case?

 

[majakdragon]

Sounds more like a partially clogged main drain. It can back up and block the vent pie. Washers put out a lot of water in a short period of time. This is why newer codes require 2" instead of 1-1/2" discharge piping for them.