John Koeller
Koeller & Company
Office 714.777.2744
Mobile 714.757.0679
Bill Gauley
Gauley Associates, LTD.

Plumbing Efficiency Research Coalition


Reduced water demands from these efficient products (as well as the conservation practices adopted by the users) definitely result in reduced wastewater flows.  Thus far, though, there are few authoritative (non-anecdotal) reports of high-efficiency products causing building drainlines or municipal sewer systems in the U.S. to experience blockages.  However, research in Australia and Europe indicates that, in the future, the combination of significantly reduced wastewater flows from a wide array of high-efficiency products and systems might result in waste transport problems in some types of U.S. building drainlines.  As more efficient practices and equipment become mainstream tools for reducing water consumption, North America must be prepared for these potential 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 leading organizations, each with a strong commitment to water efficiency and the integrity of building infrastructure.  Those organizations are:

Initially, the PERC  identified four potential target areas for possible research:

  • Drainline transport of waste related to commercial-industrial applications
  • Water reuse systems & applications (graywater & rainwater)
  • Non-water urinals
  • Sizing of efficient plumbing systems

The PERC member organizations decided in 2010 that the highest priority area for research is waste transport in commercial-industrial building drainlines.  The scope and PERC Phase 1 test plan of research has been funded and work is completed.   A narrative description of the background to the PERC research program, as well as recent press releases and articles, will provide further information.

Now Available: Download PERC Study Phase 1 
final report version 1.1 
Also download the PERC Study Data File here (1.4mb)

Now Available: Download PERC Study Phase 2 and 2.1 Final Report (1.3 mb)

The PERC Phase 2 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.

The Phase 2.1 supplemental report (which is Appendix D to the Phase 2 report) focuses on two previously unaddressed areas of study — (a) the implications surrounding dual flush toilet discharge patterns, comparing results to single volume flush toilets of comparable flush volume, and (b) on the impact of drainline slope deviations on the transport of solid waste.

Read the PERC press release on the Phase 2 study report.

Read this excellent summary of the PERC study report #1 by Julius Ballanco, P.E., in PM Engineer magazine:  "PERC study produces interesting results"





(1) 2010 - Watersmart Innovations - October 2010 (1.2mb) 
(2) 2011 - Watersmart Innovations - October 2011 (6.5mb)
(3) 2012 - Watersmart Innovations - October 2012 (2.2 mb)
(4) 2015 - Watersmart Innovations - October 2015 (3.0 mb)

Dr. Steve Cummings presentations on drainline carry  issues -
(1) 2010 - Dr. Steve Cummings presentation on drainline junctions and impacts of toilet paper (5mb) 
(2) 2013 - Dr. Steve Cummings update presentation on drainlines and toilet paper (5.4mb)

CIBW62 2009 on BUILDING DRAINS (Düsseldorf, Germany) presentations and reports on drainline carry issues -
(1) Prof. Dr. John Swaffield report on "Dry Drains: Myth, Reality, or Impediment to Water Conservation"(1.4mb) 
(2) Prof. Dr. John Swaffield presentation on "Dry Drains: Myth, Reality, or Impediment to Water Conservation"(13.2mb)  

DRY DRAINS FORUM 2009 (Frankfurt, Germany) presentations on drainline carry issues - 
(1)  Prof. Dr. John Swaffield presentation introducing the Forum (3.3mb)  
(2)  Don Boynton presentation on sustainable future (1.6mb)
(3)  Prof. Dr. Mete Demeriz presentation on dry urinals (NOTE: 21.5mb)
(4)  Ron George presentation on water efficiency and dry drains (1.1mb)
(5)  Dr. Steve Cummings, Jeff Clark, and Les Barnard joint presentation "Performance Compatibility of Water Efficient Fixtures with Drainage Systems and Plumbing Codes" (NOTE: 62 pages, 22mb)
(6)  Prof. Dr. John Swaffield presentation closing the Forum (1.2mb)

Press releases and articles relating to PERC-



December 2010:  PERC joins with Australia's ASFlow in an historic agreement to collaborate on DRAINLINE RESEARCH

On December 3, 2010 the Plumbing Efficiency Research Coalition (PERC) and the Australasian Scientific Review of Reduction of Flows on Plumbing and Drainage Systems (ASFlow) Committee signed an historic Memorandum of Understanding (MoU) at U.S. EPA headquarters in Washington D.C. Both organizations are working on research programs that seek to investigate the impact of reduced water flows in sanitary drainage systems resulting from reductions in water use from plumbing fixtures and fittings, appliances and commercial and institutional equipment.  Download the MoU here (2mb).