Recently there was a discussion within the ASPE Connects Open Forum regarding “Venting Vertical Offsets in Sanitary Drainage Piping.” As part of that discussion, Mr. James Richardson, plumbing inspection supervisor for the City of Columbus, Ohio, threw out an interesting point to the discussion. It is a consideration that many design professionals may have not considered in their designs as plumbing engineers generally think in terms of design within the building envelope.
So where does a sanitary plumbing system begin and end? As design professionals, our first and primary obligation is the protection of public health, safety and welfare above all other concerns. When one thinks of a sanitary plumbing system, it is generally confined to the Drainage, Waste, and Vent (DWV) system within the limits of a 30-inch boundary around the building envelope. Yes, 30-inches, although we normally use 5 feet to transition between the “building drain and building sewer.” The “5-foot rule” is little more than a “gentlemen’s agreement” that has evolved through the years within our industry. The typical code-in-force defines the transition between the drain and sewer as 30-inches. It is also normal industry practice to separate the interior plumbing system from the site, civil system at that same 5-foot point. This separation point also separates the plumbing consultant from the civil consultant.