Let us get down in the dirt, or at least “backfill.” A recent discussion on ASPE Connect’s “Open Forum” was entitled “Minimum Pipe Cover when Calculating Invert Under Building Slab for PVC Sanitary.” The post related to the conflicting information received when reviewing inverts with plumbing contractors. So the question became: “When running horizontal drains (whether they be sanitary or storm) underneath a building slab, is there a typical minimum burial depth or pipe cover required? Or is it acceptable to locate the piping tight to the underside of the slab?”
So, where shall we begin the discussion? As with any design project, one must deal with the specifics of that project and the site conditions. No code, standard or manufacturer’s installation instruction can cover or address all of the potential complexities of those specific site and project conditions. As a design professional, one must consider the information provided by the codes, standards and manufacturers’ installation instructions while applying sound engineering judgment.