Per capita water demands have been declining across North America for more than 20 years. While lower water demands result in lower wastewater flows, there are few authoritative (non-anecdotal) reports of lower water demands causing blockages in building drainlines or municipal sewer systems. However, research in Australia and Europe indicates that significantly reduced wastewater flows might result in waste transport problems in some types of U.S. building drainlines. As water demands continue to decline, North America should be prepared to address drainline issues, particularly in commercial and industrial applications.

The Plumbing Efficiency Research Coalition (PERC) was formed through an initiative led by IAPMO in 2009, and is currently comprised of six organizations, each with a strong commitment to water efficiency and the integrity of building infrastructure.

• IAPMO – International Assoc of Plumbing & Mechanical Officials
• ICC – International Code Council
• PMI – Plumbing Manufacturers International
• PHCC – Plumbing Heating Cooling Contractors National Association
• AWE – Alliance for Water Efficiency
• ASPE – American Society of Plumbing Engineers (added in 2011)

In 2012, PERC released a report outlining the results of their research regarding waste transport in commercial-industrial building drainlines – The Drainline Transport of Solid Waste in Buildings.

In 2016, PERC released a supplemental report – The Drainline Transport of Solid Waste in Buildings – Phase 2.  This report reveals important (and surprising) research findings related to the reduction of building drainlines from 4-inch diameter to 3-inch diameter, as well as findings related to 1.0-gallon (3.8-litre) toilet flush volumes in commercial installations.