Research shows that dual-flush toilets in non-residential settings are not using the partial-flush as anticipated.

Measures to improve water efficiency, including limitations on full-flush volume for toilets and use of municipal reclaimed water for irrigation, are being proposed for a green building standard.  

ANSI/ASHRAE/USGBC/IES Standard 189.1-2011,Standard for the Design of High-Performance, Green Buildings Except Low-Rise Residential Buildings, provides a design standard for those who strive for high performance buildings. It covers key topical areas of site sustainability, water-use efficiency, energy efficiency, indoor environmental quality and the building’s impact on the atmosphere, materials and resources.   

The changes regarding water are proposed via addendum v, which is open for public review until Jan. 14, 2013. To comment on the proposed changes or for more information,  

The addendum would limit the full-flush volume for all toilets to 1.28 gal per flush and limit kitchen faucet capacity to 1.8 gpm. Research shows that dual-flush toilets in non-residential settings are not used in the 2:1 full-flush to partial-flush ratio as anticipated. Instead, the full-flush option is almost always employed.  

“There is no evidence that the dual-flush toilets use significantly less water than the full-flush in commercial settings,”Thomas Pape, a member of the Standard 189.1 committee, said. “We have found that 90 percent of the flushes from dual flush toilets are full flushes. Since many models of dual-flush toilets would meet a maximum of 1.28 gal for the full flush, the maximum volume for dual-flush toilets has been decreased to match the maximum volume for single-flush toilets.”  

The kitchen faucet maximum capacity is being changed to reflect the current water efficiency standard of 1.8 gpm established by various green codes.  

Proposed addendum v also would set limits on the use of municipal reclaimed water for irrigation. Municipal reclaimed water is highly treated, usually to drinking water standards, and often in short supply. Furthermore, the growing use of municipal reclaimed water for groundwater recharge of potable water supplies increases its value.  

“It is unreasonable to allow the unfettered use of reclaimed water, considered a precious resource, as a means to save energy when there are more viable alternatives,” Pape said. “Therefore, the use of municipal reclaimed water would be prohibited for roof-cooling applications and for permanent irrigation of vegetated roofs using either in-ground or above-ground irrigation systems. There are many other alternative water sources that can be used for this puprpose, including graywater, condensate recovery, rainwater and cooling tower discharge.”  

Its temporary use in above-ground irrigation systems is allowed, however, during the vegetation establishment period required for vegetated roofs.

For more information on the other addendums for public review,

Source: ASHRAE