IAPMO Water Demand Calculator

We did the math: correctly sized plumbing pipes reduce construction costs and address water aging

Plumbing systems in new home construction are routinely overbuilt, increasing housing costs because the most commonly-used pipe sizing formula is almost 90 years old – developed well before today’s innovative low-flow fixtures and appliances came on the scene.

Using the IAPMO Water Demand Calculator for new residential construction reduces water aging, delivers hot water faster, generates significant construction cost savings, and saves water and energy. A study by the engineering firm Arup found that using the IAPMO Water Demand Calculator saved an average of 500 gallons per dwelling unit per year Which means a development of 25-30 new homes would save the average residential swimming pool-worth of water every year.

Unnecessary New Home Construction Costs From Outdated Pipe Sizing

UP TO $4,500 FOR NEW SINGLE-FAMILY

home meter connections

UP TO $250 per year

in water and sewer charges

UP TO $2,500

more in piping costs per home

Savings in New Home Construction From Proper Pipe Sizing

Single-family Home

The total average savings for a typical single-family home can exceed $2,000 and can be as high as $5,000, depending on location.

45-unit Multi-family Building

The potential savings are even higher and can exceed $100,000 on a 45-unit multi-family building, especially where utility meter connection fees are high due to water scarcity.

200-unit High Rise Apartment

Could see about $250,000 in water plumbing system construction savings, while the owner could save over $10,000 per year in water and sewer charges.

Excessive construction and meter connection costs are just the beginning. Oversized pipes just don’t work as well with today’s high-efficiency fixtures and appliances.

Hot water taking too long to get to your shower? Large-volume pipe diameters cause hot water delivery delays to low-flow fixtures. Even worse are the risks of water-borne pathogens from water aging and stagnation in oversized residential water pipes.

Problems With Outdated Pipe Sizing

OVERSIZED PIPES

increase the wait time for hot water to arrive at your faucet or shower

STAGNANT WATER

increases the risk of bacterial growth which can lead to diseases like Legionnaire’s Disease (Legionella Pneumophila)

MORE EXPENSIVE

for homebuilders and consumers

The IAPMO Water Demand Calculator accurately predicts peak water demand in single-family homes and apartment buildings, reducing the carbon footprint of the structure and saving consumers on both their water and water heating-related energy utility bills for the entire life of the plumbing system.

Benefits of Proper Pipe Sizing

WATER & ENERGY CONSERVATION

Improved water conservation and energy use

AFFORDABILITY

Improved housing affordability with reduced cost of building materials and meter fees

WATER QUALITY

Improved water quality and public health

IAPMO Water Demand Calculator Success Stories

Villara Leads the Way as Early Adopter of IAPMO’s Water Demand Calculator

Based in Northern California, Villara Corporation has been using the Water Demand Calculator for more than five years. More than 5,000 single-family homes have been built using its calculations

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Seattle Advances Water Demand Calculator Use with Training

With an eye toward Seattle mandating use this year of IAPMO’s Uniform Plumbing Code (UPC®) Appendix M — the Water Demand Calculator® — for multifamily buildings, the county and local ASSE and IAPMO chapters recently held an in-person training for inspectors, installers and design professionals.

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Vancouver Leads the Way on IAPMO’s Water Demand Calculator

Since spring of 2023, contractors and builders in the city of Vancouver, British Columbia, have the option to use IAPMO’s Water Demand Calculator™ for potable water systems, a money-saving alternative to conventional pipe sizing that will also reduce the amount of stagnant water in pipes.

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The Science Behind More Resilient Communities

IAPMO, a global team of experts, engages industry and governments to tackle some of the world’s most significant challenges to create a safer built environment.

Whether it’s building more resilient communities, saving costs without compromising the quality of home and commercial buildings, bringing more sustainable products to market, or protecting public health and safety, IAPMO expertise and research-backed initiatives create sustained impact.

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