November 19, 2025
New PPFA Study Shows Rightsizing Piping Systems Improves Water Quality
By Alex Gross
A new study from the Plastic Pipe and Fittings Association (PPFA), conducted by Drexel University, points to rightsizing piping systems to optimize flow velocity and improve water quality.
The study, “Premise Plumbing Flow Rates, Linear Velocity, and Nitrification,” marks an important step in the industry. This scientific research promotes accurate plumbing design in model codes by revealing the safest, most appropriate pipe sizing for North American water distribution systems.
The Drexel research team conducted a variety of tests on copper, PEX, and CPVC piping to understand how different flow velocities impact biofilm activity, nitrification, and emission pathogens. They obtained their results by flushing the pipes five days a week or once a week, then analyzing the water.
The research found that rightsizing piping systems correlated with better water quality, higher residual disinfectant levels, less degradation of ammonia, lower turbidity levels, and lower adenosine triphosphate (ATP) levels, which indicate the presence of microorganisms.
Biofilm was best controlled on 3/8" or smaller diameter pipes with rebalanced velocity. The study also emphasized the importance of frequent flushing. All pipes, regardless of material, reached a similar level of disinfectant loss when they were not flushed frequently.
The study also noted that copper might selectively favor the growth of opportunistic pathogens, such as legionella. Additionally, in low-use conditions, cloudiness and opaqueness (turbidity) were substantially higher in copper pipes compared to PEX and CPVC.
Ultimately, deciding on the ideal plumbing system design involves weighing multiple factors, including cost, durability, and water quality considerations.
GF collaborated with PPFA to conduct project work for this study and is supportive of the outcomes of the study as well as its conclusions on how to build a better plumbing system.
The study, “Premise Plumbing Flow Rates, Linear Velocity, and Nitrification,” marks an important step in the industry. This scientific research promotes accurate plumbing design in model codes by revealing the safest, most appropriate pipe sizing for North American water distribution systems.
The Drexel research team conducted a variety of tests on copper, PEX, and CPVC piping to understand how different flow velocities impact biofilm activity, nitrification, and emission pathogens. They obtained their results by flushing the pipes five days a week or once a week, then analyzing the water.
The research found that rightsizing piping systems correlated with better water quality, higher residual disinfectant levels, less degradation of ammonia, lower turbidity levels, and lower adenosine triphosphate (ATP) levels, which indicate the presence of microorganisms.
Biofilm was best controlled on 3/8" or smaller diameter pipes with rebalanced velocity. The study also emphasized the importance of frequent flushing. All pipes, regardless of material, reached a similar level of disinfectant loss when they were not flushed frequently.
The study also noted that copper might selectively favor the growth of opportunistic pathogens, such as legionella. Additionally, in low-use conditions, cloudiness and opaqueness (turbidity) were substantially higher in copper pipes compared to PEX and CPVC.
Ultimately, deciding on the ideal plumbing system design involves weighing multiple factors, including cost, durability, and water quality considerations.
GF collaborated with PPFA to conduct project work for this study and is supportive of the outcomes of the study as well as its conclusions on how to build a better plumbing system.