I realize this has been discussed here before but my case seems a
little different in that both of the following happen to me:
When the washing machine drains the tiolet bubbles - and sometimes it
fills up with water and sometimes it emptys almost completely.
Either a vent clog or a drain clog or both right?
The overfilling sounds like a clog and the draining seems like some
type of siphoning effect due to a clogged vent.
These are the only appliances on this drain line (washing machine,
tiolet, sink) all the way to just before the septic tank so other
items in the house do not affect this.