#USA #Philadelphia #Water Quality #Plumbing Study #Pipe Design

Understanding the Impact of Flow Velocity on Water Quality

A recent investigation conducted by the Plastic Pipe and Fittings Association (PPFA) in collaboration with researchers from Drexel University has shed light on an essential factor affecting water quality in buildings: flow velocity. Published in the latest issue of the American Water Works Association's journal, AWWA Water Science, this study emphasizes the significant role that higher flow velocities and appropriately sized plumbing systems play.

The Study's Foundations

The research, titled "Premise Plumbing Flow Rates, Linear Velocity, and Nitrification," represents a vital step toward achieving a better understanding of water distribution systems in North America. The goal is to offer clear and comprehensive scientific insights that can lead to improvements in plumbing designs within existing model plumbing codes.

Drexel University's research team explored various factors linked to water safety and biological activity within plumbing systems. Critical elements included the relationship between flow velocity, biofilm activity, and nitrification processes—specifically the oxidation of ammonia and the potential release of pathogens from pipes. The study involved testing several pipe materials, including copper, PEX, and CPVC, under different flushing frequencies.

Key Insights and Findings

One of the notable conclusions drawn from the study is that elevated flow velocities tend to enhance water quality significantly. Higher flow rates correlate with increased residual disinfectant levels, reduced ammonia degradation, and lower turbidity, which measures water cloudiness. Additionally, decreased levels of adenosine triphosphate (ATP)—a marker for microbial presence—were observed, suggesting that fast-flowing water is effective at scouring biofilm and limiting nitrification.

Interestingly, the most pronounced improvements in managing biofilm appeared in smaller diameter pipes (3/8 inches) when combined with high flow velocities. This finding highlights the importance of pipe sizing in conjunction with flow rates for achieving optimal water quality.

Moreover, the frequency of flushing water systems emerged as a crucial factor, with the study indicating that pipes flushed only once a week experienced similar levels of disinfectant loss and nitrification, independent of the pipe material or diameter. This finding underscores the need for regular water use or flushing to prevent stagnation and subsequent degradation in water quality.

While the research suggests that copper pipes can impede microbial growth, researchers also noted a caution: under certain conditions, copper could promote the growth of opportunistic pathogens, including Legionella. In low-usage scenarios, cloudiness levels were significantly higher in copper pipes compared to PEX and CPVC.

Industry Expert Commentary

Mike Cudahy, Codes and Standards Specialist at the PPFA, expressed optimism over the study's impact, stating, "The study clearly demonstrates that flow velocity in plumbing systems is a critical factor in maintaining water quality and provides significant evidence for pipe selection. We hope it will serve as an aspirational starting point for future scientific studies by other researchers to focus tests on realistic water sources and plumbing scenarios."

The Path Forward

Although the study provides valuable insights, further research is required to confirm its findings across various plumbing designs and conditions. Additional factors, such as water temperature and environmental effects, need to be investigated to develop evidence-based guidelines for plumbing system design and operation.

About the Organizations Involved

The Plastic Pipe and Fittings Association (PPFA) has been representing manufacturers and suppliers of plastic piping systems since 1978. Working closely with regulatory bodies, the PPFA aims to establish and promote effective standards and regulations in the industry. Drexel University, ranked among the top 100 universities in the United States, focuses on innovation, community engagement, and applied knowledge in its research and educational efforts.

For more information on their findings and initiatives, visit PPFA's official website.