The U.S. has experienced a drop in water usage per capita over the last two decades. As an example, from 2005 to 2015, a significant decline in surface freshwater withdrawals was observed in 64% of counties, paralleled by a 10% drop in household water use, despite an 8% population increase.^[i] The efforts made to create and distribute water efficient plumbing products by the plumbing supply-chain has contributed significantly to this reduction of water usage. An example of the impact of the water efficient plumbing products, Plumbing Manufacturers International (PMI) estimates that WaterSense certified products have saved more than $135 billion in water and energy expenses over the past decade.

If you are reading this article you are more than likely a member of or associated with the plumbing supply-chain serving the U.S. market. Congratulations on a job well done! However, are work is not done. As an example, based on the potential impact of climate change, counties in the U.S. having a high or extreme risk of water shortages will increase from 10% of counties today to 32% by 2050.^[ii]

A significant driver of water efficiency are the plumbing standards and codes developed and used throughout the U.S. The intent of this article is to provide the reader with an understanding of trends occurring in the development of codes and standards related to water efficiency and how those trends might impact the plumbing system supply-chain and the products and services delivered.

Plumbing fixtures

The plumbing fixture industry has been at the leading edge of driving water efficiency for many years. Since the Energy Policy Act was implemented in 1994, all plumbing products sold in the United States must meet water-efficiency standards. These standards now are a maximum of 1.6 gallons per flush (gpf) for residential toilets, 2.2 gallons per minute (gpm) for residential kitchen and bathroom faucets, and 2.5 gpm for showerheads. In addition, the plumbing industry supports the voluntary federal EPA standards and certification program WaterSense which sets water efficiency levels at least 20% below the mandated Federal regulations.

A June 2019 report by GMP Research and commissioned by PMI estimates that 81.4 percent of installed toilets in America meet federal water-efficiency standards and that virtually all installed showerheads and bathroom faucets meet the standards. The report also includes national and state data about the use of WaterSense products, which use at least 20% less water than products meeting federal standards. For example, WaterSense-certified tank-type toilets have 16.8 percent market share nationwide. WaterSense-certified bathroom sink faucets have 40.1 percent market share, and WaterSense-certified showerheads have 45.4 percent market share.^[iii]

National model plumbing codes set water efficiency requirements for plumbing fixtures based on Federally mandated requirements since the codes are written to provide minimum requirements. Water efficiency codes and standards written to drive requirements beyond the minimum Federal requirements often require compliance to the U.S. EPA WaterSense Program. In addition, states currently dealing with water shortage issues have adopted requirements based on the U.S. EPA WaterSense program.

Over several code development cycles, including the current cycle for the 2027 publication, proposals have been submitted to revise the model plumbing codes to cite the U.S. EPA WaterSense Program requirements. These proposals have not been successful to date, and I do not anticipate they will be successful in the near future. The opposition to lowering the water efficiency requirements below the Federally mandated requirements on a national scale is based on a lack of understanding of the potential impacts of the lower water volumes on the waste flow downstream of the plumbing fixtures. Until research is initiated to determine the overall effect, there is little support for going lower than the currently mandated requirements except in regions of the country where water shortages have reached crisis levels.

Where there may be an impact on the future market for water efficient plumbing fixtures is the installation of water efficient plumbing fixtures complying with Federal regulations into existing commercial and residential facilities not currently in compliance with the Federal regulations.

A 2017 study, sponsored by the Alliance for Water Efficiency and PMI, focusing on Arizona, California, Colorado, Georgia and Texas – all states that have experience water shortages - showed that between 90 billion and 170 gallons of drinking water could be saved per year in the five states with the installation of water efficient toilets in residential properties not currently using water efficient toilets. These savings for the five-state region can be extrapolated to 360 billion gallons of water per year saved nationally.^[iv]

In addition, PMI commissioned a study in 2022 that analyzed took the market penetration of WaterSense certified toilets having a 1.28 gallons per flush in California, an area with significant water shortage issues and where the requirements for a 1.28 gallons per flush is mandated. The market penetration in the State ranges from 22.0% to 25.9%. The market penetration in disadvantaged communities was even lower, ranging from 19.6% to 22.2% in the five regions. The study concludes that should California do a toilet replacement program focused on solely disadvantaged communities, 3.2 billion gallons of water can be saved in three to five years.^[v]

PMI has developed a Legacy Product Replacement initiative which provides excellent information on their website related to the development and implementation of legacy product (inefficient toilets and other fixtures) replacement programs. I encourage distributors and other members of the plumbing supply chain to review the PMI information to see if a program exists in your area and if not, how you might work to develop one. To read more about this PMI initiative please visit their website by clicking here.

New standards published or under development related to plumbing fixture water efficiency include the following:

• IAPMO Z1398 Recirculating Shower Systems which covers portable and stationary recirculating shower systems intended for new and retrofit residential, commercial, RV and trailer applications (currently under development);
• ISO 31600: Water efficiency labelling program- requirements with guidance for implementation. The US industry and other stakeholders were well represented in the development of this international standard and through our engagement, it was ensured that the current U.S. practices were incorporated into the International Standard (currently under final review prior to publication); and
• In November, 2024 the U.S. EPA WaterSense Program released a new specification for Point-of-Use Reverse Osmosis Systems and is considering the development of the following new standards: Private-Use Lavatory, Public Lavatory, and Kitchen Faucets; and Spay Sprinkler Nozzles.

In summary, I do not see significant changes to the current codes and standards related to water efficient plumbing fixtures. Where change may occur is new state legislation proposing to mandate the U.S. EPA WaterSense efficiency levels over the Federally mandated requirements. In addition, I anticipate increased activity in the replacement of non-water efficient fixtures in existing commercial and residential residences not currently in compliance with the Federal or state mandated requirements.

Plumbing system pipe sizing changes

The successful savings in water usage, driven significantly by members of the plumbing supply chain, has created the need to reevaluate how we design plumbing systems and the pipe sizes needed in those systems. The current pipe sizing requirements in model codes is based on Hunter’s Curve developed by Roy Hunter for the National Bureau of Standards (now the National Institute of Standards and Technology) in December 1940. Due to the decreased water usage due to the use of water efficient plumbing fixtures and other water saving initiatives, the basis for Hunter’s Curve have become obsolete and lead to designs using significantly larger pipe sizes than needed causing decreased flow, increased water aging times, potential stagnation and ultimately public health issues.

IAPMO, a developer of model codes and standards, is the developing organization overseeing the development and maintenance of the Water Efficiency and Sanitation Standard (WE-Stand). IAPMO took the lead in developing a new statistically based pipe sizing method for single and multi-family dwellings which resulted in the creation of the Water Demand CalculatorÒ. The Water Demand Calculator was adopted into the 2023 revision of WE-Stand. In addition, the California Building Standards Commission approved the adoption of the Water Demand CalculatorÒ into the California Plumbing Code as an alternative approach for pipe sizing beginning July 1, 2024.

The Internation Code Council (ICC) is in the process of developing a standard (ICC 815) establishing a comprehensive design methodology for sizing water distribution, sanitary drainage, and vent piping systems for residential, mixed-use, and institutional buildings. In addition, ICC is in the process of developing a standard (ICC 820) intended to establish uniform approach to monitoring and collecting data for water supply and sanitary drainage systems in residential, multi-family, mixed use, institutional, healthcare facilities and commercial buildings.

I anticipate that these new plumbing system sizing methods and monitoring programs will become increasingly used in the market place and ultimately adopted into model codes in the not to distant future. The impact of these new design platforms will be a change in pipe sizing needs and ultimately, decreased construction costs in addition to protection of public health.

Increased on-site technology for water re-use

A significant amount of my code and standards activity time related to water efficiency issues is devoted to the development of requirements for the increased use of on-site water re-use systems used both in commercial and residential applications. These on-site systems include both the treatment of waste water for recycling into gray water applications and also the treatment of waste water for use in drinking water applications. These new technologies are becoming increasingly used, especially in regions where water shortages are at a crisis level. As one can imagine, the increased use of these treatment systems in on-site applications requires new knowledge and expertise at both the distributor and contractor section of the plumbing supply-chain to ensure the end user is provided sufficient information and guidance on how to manage the systems.

The following are recent code and standards updates and projects under development in this area:

• The 2024 publication of the IAPMO WE-Stand includes the following updates:

  • Updated ecological-sanitation system provisions addressing the operation and maintenance of urine storage tanks and treatment and application of stored urine.
  • New Chapter 9 for the design, installation, construction, and maintenance of gray water treatment systems for non-potable water use.
  • Updated requirements for potable water rainwater catchment systems addressing minimum water quality; maintenance and testing; collection surfaces and drainage materials.
  • New Appendix E for the design and installation of onsite wastewater treatment systems for direct potable water use in dwelling units.
  • New Appendix F for the design and installation of gray water drainage systems in new construction, additions, and retrofits to allow future connections to gray water irrigation or re-use systems.
• IAPMO has published IAPMO Z1324: Alternate Water Source Systems for Multi-Family, Residential, and Commercial Use which covers alternate water source systems intended to process water from alternate water sources such as greywater, rainwater, stormwater, air conditioning condensate, and other non‐potable reuse applications, for use in subsurface and/or surface irrigation, cooling tower makeup and toilet/urinal flushing applications, or other similar reuse applications.
• The ICC is currently developing a standard (ICC 825) providing design, construction, material, location, operation, and maintenance for residential onsite wastewater treatment systems.

The continued increase in the knowledge required to design, install and maintain these new treatment systems has generated activity in the development of personnel training/certification programs. Below are examples of current programs and planned activity in this area:

• The Water Quality Association (WQA) has been a leader in developing training/certification programs related to water treatment systems. Examples of the certification programs they currently offer are: Water Treatment Representative; Water Specialist; Installer; Treatment Designer; Service Technician; and Mater Water Specialist.
• The American Society of Sanitary Engineering (ASSE) is entering the training market related to water treatment systems. ASSE 10000: Professional Qualifications Standard for Green Plumbing Systems Installers establishes the level of competency necessary for the installation of sustainable plumbing and mechanical systems and products is being revised to include the latest trends and requirements for graywater reuse. In addition, they offer ASSE 21000 Certification for Rainwater Catchment Systems. ASSE is in the process of developing professional qualification standards for water treatment equipment personnel; the standard is going through the national accreditation process but has net yet achieved an American National Standard designation.
• ICC is in the process of developing ICC 1600 - Professional Qualifications Standard for Onsite Direct Potable Water Reuse Systems for individuals involved in the design, plan review, installation, inspection, auditing and training of onsite direct potable water reuse systems.

The questions I pose to members of the plumbing supply chain are;

1. Are we prepared to serve the market with these new technologies and provide the distribution chain for these products at the local level?
2. Do we have trained qualified staff on board that can address client/customer questions and concerns related to the products we are providing to the market?

Whole House certification for water efficiency

There are several voluntary certification programs using consensus based standards that provide labeling for new home construction that are focused specifically on water efficiency requirements. These programs include:

• The U.S. EPA WaterSense Program offers a home certification program that validates the home is designed to use at least 30% less water than a typical home anywhere in the country;
• The National Green Building Standard;
• Certified Water Rating Index;
• Water Efficiency Rating Score; and
• HERSH2O

The National association of Home Builders provides a good summary of the various programs listed above and I recommend you go to the NAHB website for further information.

I do not anticipate these programs being eventually mandated into model code requirements. However, they do provide an excellent way for home builders/developers to help market the water efficiency of their homes through a third-party validation service.

In conclusion, water shortage issues are growing and anticipated to spread to other areas of the country. We need to be positions to advocate and work with our local government bodies to ensure existing water efficient products we have in our distribution locations are installed in existing buildings and residences creating a positive impact on water savings and cost to the public.

In the future, the codes and standards community are working to ensure new water efficient products and systems meet minimum public health requirements while also decreasing water usage.Our world is changing and the types of products our industry will be asked to provide to the market and the expertise to deliver those products to the customer are changing. The U.S. plumbing supply chain is well suited to deliver these products but we all need to be anticipating change and be proactive in ensuring we continue to play a major role in ensuring adequate water supplies for future generations.