Your home's plumbing system could be driving up costs in ways you've never considered. Construction expenses, wasted water, higher utility bills, and even health risks can all trace back to pipes that are bigger than necessary.
Most plumbing systems in the United States are designed to handle flow rates far higher than what a typical household uses. The original sizing standards date back to the 1940s and were based on worst-case scenarios, where every shower, toilet, faucet, and appliance might run at the same time. Those assumptions made sense when water use was less efficient, but usage patterns and fixtures have changed, while the standards largely have not.
The result has made it common for pipes to be larger than they need to be.
The Pipeline to Nowhere
This oversizing pattern has been understood in the plumbing field for years, with the core issue being the design for peak demand that rarely happens.
“You could build a 10-lane highway out to a small town for a concert that might happen once a decade, but that might not be the best use of resources, and it’s going to be very oversized,” said Christoph Lohr, Vice President of Technical Services and Research at IAPMO.
Until recently, plumbers and builders lacked a better way to calculate realistic water demand. That changed when IAPMO, the American Society of Plumbing Engineers, and the University of Cincinnati developed the Water Demand Calculator. It uses real-world water-use data to size systems more accurately.
Real Savings, Real Impact
With housing affordability under pressure, builders are looking for ways to reduce costs without reducing quality.
“Every cent, every percent matters at this time, with the affordability issues that are facing our nation,” said Jacob Atalla, Vice President of Innovation and Sustainability at KB Home. “This is the right time to look for new ways to save on costs.”
Studies commissioned by IAPMO show construction cost savings ranging from $500 to $1,500 per home in pipe materials alone. In some markets, where meter or connection fees are tied to pipe sizing, total savings can reach $2,000 or more per dwelling unit.
Those savings scale quickly in new communities.
Hot Water, Faster
Right-sizing can also affect daily comfort in a home.
If the pipes are smaller, then there is less water stored in them between the water heater and the faucet. This means v arrives more quickly, and since there is less wait time, there is also less water wasted.
“The studies that I’ve seen show that there is probably about an additional 500 gallons per year that can be saved in a single-family detached home,” Atalla said.
The Stagnant Water Problem
Oversized pipes can also be a health hazard.
“When water is sitting there too long, we’re also increasing the likelihood of having issues with water quality,” Lohr said.
Water that sits still loses the disinfectant protection that is added at the municipal level. When water sits and warms to room temperature, it can create conditions where bacteria can multiply. One example is Legionella, the bacteria that causes Legionnaires’ disease, which is known to thrive in warm, stagnant plumbing systems.
Right-sizing keeps water moving more frequently, which helps maintain disinfectant levels and reduces the chance for bacterial growth. It also means the water reaching faucets and showers is fresher and closer to the temperature it should be.
Making It Happen
Right-sizing only works when the design team, trades, and local officials are aligned.
“It starts with the municipalities,” Atalla said. “But then it continues to the trades and the contractors that we work with to get it done.”
As adoption of the Water Demand Calculator expands, right-sizing becomes easier to standardize across communities and plan sets because it does not require changes to materials, labor skills, or installation practices.
“The plumbing industry is ready to utilize it,” Lohr said. “It’s more just knowing the right people.”
The Bottom Line
Right-sizing is not about cutting corners. It is about using better data to design a system that matches how people actually live. In today’s market, anything that improves performance while reducing cost is highly valuable.
“Everybody loves green, but it’s the green dollar in their pocket that first comes to mind, and then maybe green building after that,” Atalla said. Right-sizing:
Lowers construction cost
Reduces wasted water
Improves daily comfort
Supports healthier building systems
For homeowners, it means faster hot showers, less water wasted down the drain, and cleaner, fresher water in the fixtures they use every day. For builders, it is a way to reduce costs without sacrificing comfort or performance.
Michael Letendre
Michael Letendre is a writer for NewHomeSource and Builder Magazine.