To obtain LEED Zero Water certification, a project must achieve a potable water use balance of zero for the past year.
Water Balance = Total Potable Water Consumed – (Total Alternative Water Used + Water Returned to Original Source)
An overview of the water balance is provided in Table 3.
“Water returned to its original source” includes rainwater stored and infiltrated or evapotranspirated via green infrastructure, and wastewater treated and returned to the local watershed or aquifer via decentralized wastewater treatment systems. Calculations for the amount of rainwater retained and infiltrated on-site must be based on the calculation methodology outlined under LEED v4 Sustainable Sites credit Rainwater Management.
Table 3. Water Balance