Appendix M of the IAPMO Uniform Plumbing Code, or the Water Demand Calculator, was integrated into the California Plumbing Code on July 1. It provides a new method for sizing water pipes in residential buildings. For Villara Corp., a leading plumbing and HVAC contractor in Northern California, it remains business as usual, having used the calculator for over five years to construct over 5,000 single-family homes.

The IAPMO Water Demand Calculator has faced challenges due to exclusions from its documentation and calculations, causing difficulties for engineers in luxury apartment buildings.

When a plumbing engineer receives the design of a health care building — our minds gravitate to designing the system to optimize all the different considerations I mentioned above — with the fixture layout the architect has developed. But what if the layout changed? What if the amount of fixtures were reduced? 

The Water Demand Calculator has been adopted in several states and cities, including California and Seattle, and is expanding peak flow rate calculations into commercial buildings. The future looks bright as version 3.0 is in the works for commercial buildings.

“Governmental members” may desire a public perception of having “no vested financial interest in” the development process. But there is no requirement or mandate for them to be transparent in avoiding conflicts of interest.

There is a battle going on in the industry when it comes to domestic water distribution systems, and it lies in how plumbing engineers size domestic water piping. System longevity, pressure drop, water age, noise and building codes will influence the approach taken in sizing a domestic water system.