Summary: Interpretation ruling pertaining to establishing the calculation baseline for Water Reduction Credits 3.1 & 3.2 when on-site tests have been conducted, and demonstrate that the supply water pressure levels (psi) to the fixtures are substantially below the 80 psi referenced within the Energy Policy Act of 1992. Context: The scope of the project incorporates new construction of four residential halls on a college campus, which house more than 250 students and staff. Three of the buildings are three stories, and the other is four stories. Description: The residence halls are incorporating a range of fixtures that are below the flow rates within the Energy Policy Act of 1992 (dual flush toilets, and faucets within the kitchens, kitchenettes, bathrooms & apartments). The showers in the residence hall are the largest water consumer (by a large %) within the residence hall buildings. To begin to understand the water amount actually used on the project, the owner conducted some initial on-site tests to determine the supply pressure to the plumbing fixtures, and how that translated into the actual flow. On-site tests for one of the buildings have been conducted on the flow rates of the shower heads with the following results: Fixture type currently installed = 2.5 gpm 1st floor: 52 psi static, 2.10 gpm 2nd floor: 46 psi static, 1.92 gpm 3rd floor: 41 psi static, 1.79 gpm 4th floor: 37 psi static, 1.85 gpm Question: o Would the design case account for the lower psi (reduced water use) by multiplying the \'Water Use\' column within the calculation template by the percentage of supply/baseline? For example for a shower on the first floor the \'Water Use" would be multiplied by 65% (52/80) or by just including 2.10 gpm as the flow rate for the fixture on this floor? o What is the appropriate methodology for establishing the calculation baseline when the water pressure supply rate (psi) is substantially lower than the 80 psi outlined as the baseline flow rates under the Energy Policy Act of 1992?
[Note: this ruling was revised on 9/1/04.] The underlying assumptions used for calculating projected water use savings should remain consistent between the baseline and design case. Supply water pressure varies across the United States and within individual buildings (as you note in your inquiry). Flow rates at 80 psi are used for the calculations in this credit for consistency and to reward use of efficient fixtures. It is recommended that all projects use the flow rates reported by the manufacturer at 80 psi for comparison with the Energy Policy Act of 1992 flow rates. If you wish to use on-site tests to report the most accurate volume of water use, you must be consistent throughout all fixtures and test both baseline and design fixtures. It is not acceptable to use flow rates at 80 psi for some fixtures and actual flow rates for other fixtures. Measurement can also be used to account for the benefits of whole-building strategies, e.g., flow restrictors at the water service entrance. Applicable Internationally.