When I hear the term “luck of the draw,” I can’t help but imagine an unfortunate soul sitting at a craps or roulette table in a casino, head in hands and slot machines ratcheting in the background. It might be what the server says while handing the patron a free drink to help console that he just lost his shirt, “Well buddy, I guess it’s just the luck of the draw.” Once we’ve become sober to reality, most of us know there is indeed some probability that we’re not going to get rich at a casino. This probability is based on statistics, the collection, analysis, interpretation or explanation and presentation of data. In plumbing engineering, our mathematical model is the Hunters Curve. Published in 1940, Roy B. Hunter wrote the house rules to make sure the odds were stacked in our favor and plumbing systems would be adequately sized. He did so in a way we should all appreciate, and he passed on a responsibility to us that we should take to heart.
The “Hunter’s Curves” that we hear so much about are part of a report that were “carried on by the National Bureau of Standards, now known as the National Institute of Standards & Technology (NIST), overseen by the Federal Department of Commerce. The report itself is known as Building Materials & Structure Report BMS65, “Methods of Estimating Loads in Plumbing Systems.” At the time of its publication, you could own the report for 10 cents, the cost of playing a riverboat slot. The Plumbing Manual itself, BMS66, was double the cost at 20 cents. You can download either of those documents for free now from the NIST website. As I look through these two BMS reports, it appears that a lot of information has remained the same. Does this imply that the science used to create these charts and tables was so spot on that they just got it right the first time? Or, should we be re-evaluating the inputs that were used to create some of the information we use?