Sounds like it should work for you. I'm assuming this is temporary. You're probably required to have a vent, but it may work without it. I've got a similiar situation now. Moved the cleanout (used a saddle tee) up stream and then tapped into the cleanout w/ an adapter to 1.5" for a sink and washer. Works fine. If you do need a vent, an air admitance valve might work for you.