Premise Plumbing Modeling

The widespread provision of safe drinking water to the general population is considered one of the great engineering achievements of the twentieth century. A key element of water supply infrastructure is the premise plumbing systems (PPS). The Premise Plumbing Modeling (PPM) Task Committee was established in summer 2019 as part of the Water Distribution Systems Analysis Committee. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book covers critical aspects of PPM, including, but not limited to, demand estimation, hydraulics and water quality fundamentals, current PPM modeling capabilities and limitations, design, code, standards, operations, and instrumentation. It covers water demand, which is critical to understanding the hydraulic and water quality phenomena within premise plumbing. The book also covers the fundamental hydraulic phenomena in PPS. It discusses the range of simulation models that have been and could be applied to PPS, including their limitations.

Premise plumbing modeling entails the simulation and analysis of hydraulic and water quality conditions that exist throughout the piping network inside a building. These pipes deliver clean water to the occupants and carry wastewater away from the premises. The focus of this chapter is on the clean water component. A key aspect of the premise plumbing scenarios is modeling the stochastic water demand patterns. The chapter also focuses on indoor water use, excluding fire suppression systems. Instantaneous peak water demand is a key parameter for premise plumbing design, governing the size of service lines, flow meters, water heaters, treatment devices, pipe diameters, and other hydraulic appurtenances in the water supply system for the building. Software models (e.g., SIMDEUM) can simulate fixture-level water use on a very fine time scale (down to 1 s) based on typical occupant behavior in residential and commercial buildings.

Hydraulics plays a significant role in defining the phenomena in premise plumbing, so it is critical to have a thorough understanding to predict the water quality phenomenon at the fixture level. This chapter discusses the various hydraulic phenomena within the premise plumbing system (PPS) and water distribution systems (WDS) that have a direct impact on the integrity of PPS. It explains fundamental hydraulics in the PPS; hydraulic transients within PPSs and WDS, limitations of current modeling approaches, practical observations, and research recommendations. To measure hydraulic transient pressure variations in PPSs as a function of input parameters such as boundary head, valve positions, and transient triggering mechanisms, an experimental setup was designed to mimic the range of street-level pressures encountered in the real system. Hydraulic transients and pressure surges in water pipelines are pressure fluctuations caused by a change in flow conditions.

Water quality in buildings is complex and impacted by initial water quality and highly variable periods of both stagnation and flow. Calculating water age is the simplest of water quality problems, where water ages uniformly within a system for all pipes. This chapter discusses recent modeling efforts in PPS water quality modeling. The topic areas included in this chapter are dispersion and its impact on water quality, chemical species modeling, biological species modeling, and nonnetwork models such as data-driven or statistical modeling. The chapter provides a brief introduction to secondary disinfection and then describes disinfectant residual models that have been developed and used for pipe networks and how they might be applied for building water system modeling. It presents surveys of models for processes in the water system component portion of the exposure route. The chapter concludes with a summary of modeling needs related to PPS water quality modeling.

Hot water systems have different characteristics than cold water systems because they have hot water tanks and recirculation systems, which require various constraints such as energy use, water quality, scalding risk, and conservation issues. This chapter presents a comprehensive discussion of the special features required for dealing with hot water in premise plumbing systems, including hot water systems, recirculation systems, use of simulation modeling for energy use, and impacts of codes and standards. The state of California has a building energy efficiency standard that requires construction companies to demonstrate that a new building meets specific energy efficiency targets. The objective is to consider the impact of different types of building hot water use and distribution systems on performance in California's new buildings. The chapter also discusses the impact of codes and technology on Legionella risk, scalding risk, and energy efficiency in building water systems.

Instrumentation supports premise plumbing modeling efforts by collecting the data needed to test, calibrate, and validate models. There are many different parameters of interest in premise plumbing modeling and a variety of ways to collect the data required. This chapter provides an overview of the data needs for modeling, with considerations for selecting and collecting data using sensors. Parameters of interest for premise plumbing modeling fall into three categories: hydraulic, water quality, and energy. Parameters are discussed in terms of online, continuous monitoring, although grab samples are also an option for many of the parameters. There are several other considerations when setting up instrumentation for premise plumbing systems. These factors look beyond the parameters and sensor types to sensor design, installation, and operation. Integrating these factors within the study design framework is critical to successful data collection efforts.

Modeling premise plumbing systems requires both basic knowledge of water distribution system modeling and understanding of how premise plumbing systems work. This chapter presents a range of previously studied premise plumbing system (PPS) water quality modeling topics. Several types of hydraulic models have been applied to PPS. These include transient models, computational fluid dynamics models, demand modeling, and flow and pressure modeling. One of the first applications of modeling PPS arose because of an increased interest in water security. More recently, the emphasis in premise plumbing modeling has turned from water security-related issues to more general water quality issues. This change in emphasis was spurred in part by high-visibility issues involving chemical and microbiological contamination such as lead, Legionella, and coliform among others. The water quality modeling arena is broad and complex, and tools that link, expand, or connect these models together may be required to fully understand water quality for buildings.

Advanced smart water sensors and technologies are entering water markets, including leak detection, smart fixtures and appliances, smart filters, and bottles, tap water quality, and irrigation. In this chapter, the future of premise plumbing and modeling are discussed. Specifically, this chapter covers the use of smart water sensors/technologies in premise plumbing, new developments in information management technologies such as Building Information Modeling and Digital Twins and stakeholder engagement efforts. Past performance is not a guarantee of future results; however, it is critical to look at what is happening now and extrapolate that into the future to discuss the future of premise plumbing and modeling efforts. In the last half century or so, information management in the general field of water distribution system analysis, design, and planning has evolved significantly. Integrating emerging information management technologies with smart technologies will lead to better planning, design, analysis, management, and operational decision-making in premise plumbing.