4.303.1 Twenty percent savings. A schedule of plumbing fixtures and fixture fittings that will reduce the overall use of potable water within the building by at least 20 percent shall be provided. The reduction shall be based on the maximum allowable water use per plumbing fixture and fitting as required by the California Building Standards Code. The 20 percent reduction in potable water use shall be demonstrated by one of the following methods:
1. Prescriptive Method. Each plumbing fixture and fitting shall not exceed the Maximum Flow Rate
at ≥ 20 Percent Reduction column in Table 4.303.2; or
2. Performance Method. A calculation demonstrating a 20 percent reduction in the building “water use” baseline as established in Table 4.303.1 shall be provided. For low-rise residential occupancies, the calculation shall be limited to the following plumbing fixture and fitting types: showerheads, lavatory faucets, water closets and urinals.
COMMENTARY
Purpose:
This provision helps reduce indoor potable water use. Reduction of water use also results in decreasing the amount of energy needed to transport, process and treat water, thereby contributing to reduction of greenhouse gas emissions.
Section 4.303 provides guidelines on how to achieve a 20 percent reduction in indoor water use. There are two options to use for compliance: the prescriptive method and the performance method.
The following graphic shows the typical breakdown of indoor water use. As shown, toilets, showers, clothes washers, and faucets are the greatest indoor water users. CALGreen focuses on water use related to toilets (water closets and urinals), faucets and showers for purposes of potable water conservation
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