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Updating the Hunter’s Curve: The WDC Summit

Aug. 9, 2021
There has been widespread consensus that we have been oversizing our domestic water systems for decades.

By Christoph Lohr, P.E. CPD LEED AP BD+C

Plumbing engineers and designers have been talking about it for what seems like forever. Plumbing installers have been looking into ways to become more efficient. Plumbing manufacturers have been collecting the data to better size their equipment. And plumbing inspectors and plan reviewers have been acutely aware of the need for change for a long time. Of course, anyone in the plumbing industry knows that what I am talking about is the Hunter’s Curve. And in the US plumbing industry, there has been widespread consensus that we have been oversizing our domestic water systems for decades. While the work that Roy Hunter completed in 1940 was revolutionary for the time, we all agree that it is well past time to update the way we size these systems.

Most of the plumbing engineering industry is already aware that IAPMO, ASPE, and the University of Cincinnati collaborated to create the Water Demand Calculator—also known as the WDC—(https://www.iapmo.org/water-demand-calculator/) and that the WDC ultimately was added to the 2018 UPC as “Appendix M”. This marked the first time in almost 80 years that an alternate to the Hunter’s Curve pipe sizing methodology was added to a model code. The benefits were quickly apparent as Stantec identified in their report (https://www.iapmo.org/media/25276/water_demand_calculator_report_summary.pdf):

·       Less water stored inside plumbing systems can help improve water conservation efforts; and

·       Faster hot water delivery and improved energy efficiency;

·       Improving water quality by reducing water dwell times;

·       Up to 16% cost savings on PEX piping (based on pre-pandemic material costs);

·      Up to 11% cost savings on copper piping (based on pre-pandemic material costs);

Additionally, the Alliance for Water Efficiency (AWE) completed a study showing the incredibly positive economic impacts to home builders that reduced utility/water-meter connection fees had as a result of utilizing the WDC (https://www.iapmo.org/media/25939/awe-meter-size-connection-fee-research.pdf)

The only drawback?The Water Demand Calculator is meant to be applied only to residential buildings, either single or multi-family (such as a high-rise condo/apartment). Offices, hospitals, schools, restaurants, and other non-residential commercial buildings still need evaluation. That’s where the WDC Summit comes in: to kick start a movement. A movement that needs YOU!

On November 4th IAPMO and ASPE are hosting a virtual summit. “Updating the Hunter’s Curve: The Water Demand Calculator Summit” will hopefully be the first step in taking the Water Demand Calculator and applying it to all other building types over the upcoming years. But in the short-term, this will be a great event where participants can learn about the Hunter Curve and how it was developed, comprehend how the WDC works, and understand what steps are needed to replace our 80-year-old sizing methodology for most commercial buildings. These educational seminars will offer 0.6 CEUs (or 6 PDHs). Additionally, there will be a 1–2-hour panel discussion that will be open to all attendees to provide comments/questions and join in the dialogue. Cost to attend the summit will be $49 – this is in part to make sure all attendees have “skin in the game” into making the event a success.

In the 21st Century social movements have shifted away from being top-down. Instead, positive changes are often crowd-sourced. Grassroots initiatives are key in making changes, and for our industry to update the Hunter’s Curve likely will be no different. This is the opportunity to “crowdsource” the development of an updated “Hunter’s Curve” that our industry—engineers, installers, inspectors, etc.—having been clamoring for.  In this sense, the Summit is only the project kick-off meeting. After the summit, participants are encouraged to join the Water Demand Calculator Task Force, which will be expanding (if you want to volunteer for the task group you don’t have to attend the Summit – although we would love to have you do both!). Engineers can volunteer their time. Manufacturer can volunteer their data. If you have data or time that you can donate, we would love to have you be a part of this movement. All of us can be part of history. In this effort, we can make history together.

I’d be remiss if I didn’t add the final benefit to becoming involved in this crowdsourced effort:  the opportunity to have your name “etched in history” as it were. I’m sure many of you are like me when driving around your home city, will point out buildings to you children, your significant others, your friends, and say (with pride) “I worked on that building.”  We take pride in what we do. We make a difference in society by impacting public and health and safety through our God-given talents. This initiative takes that occurrence to the next level:  This is like-minded professionals, working hard together to achieve a purpose outside of ourselves, making history together, impacting ALL of society.This would be going from a “Hunter’s” Curve to a “Plumbing Industry’s” Curve–something we can ALL be proud of. If we make this happen together, no longer will we drive around telling our loved ones we worked on such and such building—rather we can say with confidence we made an impact to our city, state, and country. We could, in theory, point to every building under construction and say, I had a part in that. And we could tell our loved ones that we worked on a project that had a purpose outside of our day-to-day work. So come and attend the Summit. Listen and learn. Add your voice to the conversation. And then volunteer to make a difference.

Christoph Lohr has over a decade of experience in designing plumbing systems for healthcare, laboratory, hospitality, sports, and university projects. He has a reputation as a results-oriented expert. Christoph's current responsibilities as Vice President of Strategic Initiatives for IAPMO is to identify long term, high impact projects, developing a business case for them, bring resources to bear, and executing them for maximum results. He has a concentrated focus in honing his personal and organization's strategy on possible breakthrough points which has led to improved effectiveness and growth.

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