Some locales require drain water temp to be under 110 degrees. A commercial dishwasher may expel water up to 150 degrees--higher if drained right away, all tanks at once. Has the USGBC taken a stand regarding the use of drain water tempering and the potable water it uses? Thanks!
You rely on LEEDuser. Can we rely on you?
LEEDuser is supported by our premium members, not by advertisers.
Go premium for
Tristan Roberts
RepresentativeVermont House of Representatives
LEEDuser Expert
11477 thumbs up
February 17, 2012 - 2:35 pm
Suzanne, I have not seen this referenced in any LEED requirements. The typical approach is to regulate individual appliance efficiency. What you describe is similar to the issue of once-through cooling with potable water, which this credit does cover, but it's a different issue.
Narada Golden
Vice PresidentWSP Built Ecology
3 thumbs up
February 17, 2012 - 6:03 pm
Suzanne, it's a good question, drain water tempering can lead to significant water use. As Tristan mentioned, this is not referenced in any LEED requirements. The latest version of LEED BD&C 2012 does not addressed it either.
Water use from drain water tempering seems to fall outside of the water use testing criteria for the Consortium for Energy Efficiency and Energy Star, which both certify dishwasher water use.
It seems like an ideal strategy in this scenario would be adding a drain water heat exchanger to capture the heat for another use and eliminating the need for using potable water.
Suzanne Painter-Supplee, LEED AP+ID&C
PrincipalSEESolutions LLC
126 thumbs up
February 17, 2012 - 7:50 pm
Great comments. If the drain water heat recovery encompassed all hot discharge water, i.e. from steamers et al, that would be great. I researched drain water heat recovery for a utility in Canada about a year ago, but there were issues, in particular because there isn't enough water to 'get' anything out of. Waste AIR heat recovery is increasingly common in commercial warewashers, and those machines are fed with cold water. But alas, the water heated with waste air, then maintained by tank heaters, then has to be cooled! It's a problem. I wondered if a food waste digester discharge might work? (aerobic digester which converts food waste into 'water.')
Tristan Roberts
RepresentativeVermont House of Representatives
LEEDuser Expert
11477 thumbs up
August 30, 2012 - 9:16 pm
You can also get lower-temperature dishwashers, but you have to use more chemical sanitizer (chlorine, etc.), so there is a tradeoff.