I am moving my washer from one wall to another in my utility room. We are on a concrete slab and there is a 4 " sewer line just outside the new location wall that goes through my yard and ties into my main line. I plan to bust through my foundation and tie into this line installing a new service inside my wall. My concerns are how to vent this line and where to install a P trap. All help and comments are appreciatd!

Ken

Use a 4 by 3 fitting and a 3 inch trap. You will not have to vent it. You can still use a 2 inch riser.