i think its safe to say that it is pretty much a full blockage, because the water that backed up finally drained out of one of the showers, but the other one it hasnt drained... and where might i find this "test tee" you are talking about?
I just noticed today when we were doing some laundry, when the washing machine was draining, water was backing up into both showers and toilets in the house... any ideas what might be causing this??