We recently had a flooding issue with our building I live in the basement apartment, The building is 3 stories, the ceilings are approximately 10-12 feet interior 4inches subfloor ( concrete/steel ) 26-28 feet of vertical fall on a 2 inch washing machine drain to the bottom apartment. I am sure the kitchen drain is tied into this drain but the one of the ladies in the office suggested the drain was tied into the tub and showers also. (This would not be to code for a newer building I believe, I live in NC) this building was built in the 70's. Water from time to time comes out of the washing machine drain when we are washing clothes. I know water flows the path of least resistance and I was wondering if I could (rig it) with a sealed cap, so water can not go passed the opened end of the washer drain. I know the drain itself is to small to support that volume of water. Since we live in a 3 story building our apartment is the lowest point. I have found screws and angle stop handles in our toilet coming up from the line because of the pressure of falling water. My only concerns are would this then cause so much pressure it would: A. start coming out of the kitchen sink? B. damage the line in another area? C. Work and solve the problem? Not sure how the system is vented but, we normally do not have "Flooding problems." Thanks addendum: when I say (normally we don't have flooding problem) It means it's happened multiple times but not every time. Kind of an occasional problem.