Questioning Authority (Having Jurisdiction)

All U.S. consulting and specifying engineers realize their trade is regulated by codes and standards. Mechanical engineers turn to the International Mechanical Code, along with referenced standards like those developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. Fire protection and electrical engineers have the building codes and standards from the National...


All U.S. consulting and specifying engineers realize their trade is regulated by codes and standards. Mechanical engineers turn to the International Mechanical Code, along with referenced standards like those developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. Fire protection and electrical engineers have the building codes and standards from the National Fire Protection Association. And plumbing engineers have an array of plumbing codes. Codes have a purpose and they work.

However, there are three important issues about codes that the engineering community should recognize. First, the prescriptive content of a code may be inadequate for all possible cases encountered. Second, the content of a code may be incomplete—or totally silent—on important engineering criteria. Third, innovations in building technology are usually not addressed explicitly in codes, leaving design professionals in a difficult position when trying to secure authority approval for such new approaches.

Losing track of origins

Plumbing codes provide a good example of the problems blind obedience to these documents can raise. The original "Hoover Code," and the subsequent BMS 66 standards of Dr. Roy B. Hunter, established minimum design and installation requirements for indoor plumbing. Both Herbert Hoover and Dr. Hunter were engineers who based their early codes on hydraulic principles and empirical data. In turn, the written codes and standards were to be followed by installers. In effect, codes "pre-engineered" plumbing to make the craft consistent and safe.

But the engineering foundations of model, state and city plumbing codes seem to have been somewhat lost in the intervening years. The plumbing codes are no longer considered engineering tools, but sacred documents. And, to design engineers involved in real-world projects, questioning these documents can seem akin to questioning accepted dogma, rather than engaging in reasonable debate.

By all accounts, plumbing engineers and designers are very good at applying the appropriate plumbing codes. Knowing the content of each code isn't easy, and underestimating the subtleties within plumbing codes can lead to costly errors. However, being an engineer requires knowing more than the "what" of the codes—it also means knowing the "why." Having been largely trained to follow only the "what" without question, plumbing engineers have been disenfranchised by their own strict enforcement of the letter of the code. Ignoring the "why" can lead to major system problems, even if the "what" is followed obediently, as a couple of case studies prove.

When plumbing codes began requiring low-consumption toilet fixtures in the early 1990s, sizing criteria for sanitary piping was never reevaluated to ensure that carrying velocities adequate to prevent blockages could be maintained in the connected piping. In one case, a new unisex toilet room on a building's first floor was located remotely from the existing sewer piping. The designer, following the applicable code, specified a low-consumption toilet, a lavatory and a 4-in. horizontal sanitary pipe at an allowed 1/8-in. per foot, which met the invert of the existing sanitary soil pipe adequately. However, the new toilet room was prone to blockages. The single water closet, providing only 1.6 gallons of water, was incapable of keeping the long piping run washed clean.

In another example, a designer decided to install only one roof drain to handle a 40,000-sq.-ft. roof surface, but failed to consider the concept of "hydraulic head," which is the energy required for the water to flow off the roof and into the drain. The resulting calculated head, or roof depth, was 7 in.—well above the design load of the roof deck. The designer sized the drain and connected pipe only by the code's vertical pipe-sizing tables. It is possible to make poor decisions simply because the code offers no specific guidance for avoiding miscalculations.

Not knowing the "why" also can lead engineers to avoid new and innovative technologies, simply because they fear, sometimes accurately, that local enforcement authorities will not approve approaches outside the scope of written codes. However, this is not necessarily the case. For example, several jurisdictions in a number of states have permitted the use of siphonic roof drainage, an engineered-design method that takes advantage of hydraulic principles not included in the plumbing codes. (See "Defying Gravity," BD&C 06/02 p. 54, or go to )

Code officials in each of these jurisdictions were approached at the beginning of the design process. Design principles were fully explained and criteria specified. Most importantly, the engineer of record accepted responsibility for system performance and said he would submit stamped and signed drawings and calculations to the building department. In each case, the code official was open-minded, fair and even curious about the technology. As long as jurisdictional authorities were assured that a licensed engineer was in charge and the written provisions for "engineered systems" were followed, there were no objections.

These examples, with both their negative consequences and positive results, underscore the importance of knowing the "why" behind the codes we follow—and questioning the "why" to ensure our designs are complete and effective. Such understanding can even lead to the development of new technologies, if the engineer considers the code's goals and simply picks up the phone and "questions" the local authority. Engineering should rule the codes; the codes should not rule engineers.

Questioning authority should not be discouraged. It leads not to anarchy but to a deeper understanding of the engineering discipline.

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