Residential Hot Water Distribution

Distribution of hot water within residential dwellings has become one of the "hot topics" in water conservation circles (pun intended!). Many dollars spent on many consultants, resulting in many studies with many conflicting findings and all seems to have led to a great deal of uncertainty and indecision among energy and water professionals.

Questions dominate this particular building sector: Should water utilities provide subsidies for technologies that are claimed to save water? Are such claims sufficiently validated? Can existing dwellings be cost effectively retrofitted with systems that both save water and satisfy the end-user? Are there actions that can be taken with new home construction that will minimize water and energy waste?

While the Council is not able to provide answers to all of these questions (yet), we do encourage our members (and others) to avail themselves of the research and to draw their own conclusions. Thus, this page will continue to post those documents that we believe are relevant to this topic. As new research yields new information, we will make it available to you free-of-charge. If you know of or possess study reports or other documentation that you believe would contribute to the knowledge base on hot water distribution, please let us know. With permission, we will post it here. 

First check these published articles to gain an understanding of the issues…

Read Gary Klein's excellent 4-part series of articles on hot water distribution as published in the IAPMO Official Magazine:
Hot Water Distribution - Part 1 - Klein (PDF)
Hot Water Distribution - Part 2 - Klein (PDF)
Hot Water Distribution - Part 3 - Klein (PDF)
- Hot Water Distribution - Part 4 - Klein (PDF)

 Also read this very informative piece by Gary Klein and Larry Acker dealing with demand-controlled hot water distribution as published in HOME ENERGY MAGAZINE:
Home Energy Magazine - Hot Water Distribution (PDF) 


In 2002, the Santa Clara Valley Water District completed a pilot study of hot water distribution systems installed in residential dwellings.
Santa Clara Valley Hot Water Study Report (PDF)

In 2004 and 2005, Jim Lutz of Lawrence Berkeley National Laboratories issued two short pieces on (1) roadmapping a study to improve residential hot water distribution systems and (2) estimating water and energy losses within such systems:
LBNL Feasability Study - Lutz (PDF)
LBNL Estimating Losses - Lutz (PDF) 

In 2005, using funds provided through the Metropolitan Water District's Innovative Conservation Program, the City of San Diego completed a study of the Laing hot water on-demand system installed in residential dwellings.
City of San Diego Hot Water Study Report (PDF) 

Also in 2005, the California Energy Commission (CEC) released a very comprehensive report titled "Hot Water Distribution System Research - Phase 1" (200p), prepared under the Public Interest Energy Research (PIER) umbrella of CEC. This report contains extensive data on all types of piping designs and water delivery systems.
CEC-500-2005-161-Hot Water Distribution (PDF) 

In 2005, Building Sciences Corporation reported on their evaluation of the water savings achieved within a D.R. Horton home when installing and using an on-demand hot water system.
- Building Sciences Report (PDF) 

Then, in 2006, the Council conducted a summary evaluation of the potential for efficient hot water distribution systems to become a California Best Management Practice. The completed study report and the presentation by Gary Klein (CEC) on this topic may be downloaded here:
PBMP Report- Residential Hot Water Distribution (PDF)
Presentation to the Research & Evaluation Committee (PDF)  

In 2006, Lawrence Berkeley National Laboratories began a study of hot water distribution systems and the water and energy waste associated with such systems. View the project brief:
LBNL Field Monitoring Project (PDF)