When installing plastic waste piping below grade there must be a minimum __________________ clearance around the entire outer circumference of the pipe or fitting when penetrating concrete.

The requirement for a minimum clearance of 1/2 inch around the entire outer circumference of plastic waste piping when penetrating concrete is in place to allow for expansion and contraction of the piping material. This clearance is crucial because plastic pipes can expand with temperature changes and may contract as they cool. Having sufficient space around the pipe helps prevent stress on the fittings and joints, which could lead to cracking or other failures over time.

Additionally, this clearance can facilitate inspections and maintenance, as it allows for easier access around the pipe should any repairs need to be conducted. In a concrete environment, not providing this clearance may also lead to moisture retention and potential corrosion or degradation of the surrounding concrete, affecting both the piping and the structural integrity of the concrete itself.

The options presented highlight the importance of following correct installation practices as outlined in the plumbing code.