Underground plumbing Plumbing for the addition has been roughed in, and exterior insulation has been added to the foundation walls (that’s the pink stuff visible in the photos below). Next steps are inspection, backfill, and pouring the slab. The black circle at the right is the ejector pit. The addition’s basement plumbing (sinks, laundry, toilet, and shower) all tie into this. It will be connected to a junction they had previously installed in the 6″ sewer pipe.