Comparing Transient Behavior in Cold-Water Premise Plumbing Systems Designed Based on Traditional and Modern Peak Demand Estimates

The improved accuracy of modern peak water demand formulas generally results in a reduction in pipe size (diameter) in premise plumbing systems (PPS). Existing studies have highlighted the expected benefits associated with construction costs, energy consumption, and improved water quality. However, research to date has had limited consideration of the dynamic nature of premise plumbing operations, and little work has been undertaken to evaluate or quantify any unintended consequences associated with a reduction in pipe size (diameters). One consequence expected is elevated transient pressure (water hammer) responses. The current study undertakes numerical simulations to compare PPS that have pipework and components sized using traditional (IAPMO Uniform Plumbing Code) and modern (IAPMO Water Demand Calculator) peak demand formulas to quantify the changes in the amplitude of transient pressure variation and the cumulative pressure induced stress (CPIS) within the pipe network. When evaluating transient events for both a house and a residential building network, simulated transient scenarios that emulate normal operating conditions (controlled events) demonstrate that systems sized by modern peak demand estimates will have an elevated transient response, leading to an 189% increase in pressure variations (from the mean pressure), exposing systems considered to an 88–98% increase in dynamic pressure when evaluating CPIS. This highlights the value of understanding how pipes sized with modern peak demand formulas impact hydraulic transient occurrence and severity. This study serves as a foundational work to demonstrate how hydraulic transient modeling can be used to form a modeling-informed approach in the design of PPS. The proposed modeling framework can identify potential risks and assist in developing appropriate mitigation strategies for hydraulic transient events in PPS.