CalWEP Submits Comments on Indoor Residential Water Use Standard

Published: June 4, 2021

Download the letter with analysis submitted here.

The California Water Efficiency Partnership is a statewide non-profit member-based organization representing over 220 California water agencies, businesses, and other organizations. Collectively our water agency members provide services to over 6.6 million connections across the state. With a mission and commitment to maximize water efficiency, CalWEP has a deep history working on customer side conservation and efficiency programs. We believe that data-driven conservation and efficiency are paramount to ensuring that California has a reliable and resilient water future.

CalWEP appreciates the opportunity to review and comment on the Indoor Residential Water Use Study (Study). We believe the Study provides a helpful snapshot of indoor residential water use in California, along with useful information that can inform how the indoor residential water standard is set. The Study also clearly indicates where there are still big gaps in our understanding of household water use and what it will take to achieve various levels of water use efficiency on a per capita basis across the state.

As noted, CalWEP supports maximizing urban water efficiency and conservation and thus appreciates how the Study summarizes the findings of several technical studies which contain water use data and information to evaluate where we are with regard to indoor water use, and what it may take to lower our statewide average indoor water use substantially in coming years. The Study is expected to include the “information necessary to support a lower indoor residential water use standard that appropriately reflects best practices” (Water Code §10609.4(b)(1)). This focus on an evidence-based approach includes information on the ways the best practices implemented by water suppliers (such as fixture and appliance rebate programs, conservation education, and leak detection programs) -- combined with changes in customer behavior -- has resulted in reduced indoor water use statewide.

But it is also clear from this study that actual indoor water use continues to vary across the state geographically, by residence type and age, due to other factors that this report was not able to identify. This results in significant variation in the average indoor gallons per capita per day (GPCD) of water suppliers statewide.


CalWEP is concerned that the issues of technical feasibility and local cost effectiveness have not been adequately addressed in this study. We believe that the study does clearly lead to a conclusion that achieving an average indoor use of 42 GPCD at a utility scale by 2030 will require the vast majority of residences in the state to be equipped with a 1.28 gallon per flush toilet or better, and high-efficiency clothes washers. In addition, residential leaks will need to be substantially reduced, requiring almost universal use of high-frequency flow monitoring technologies (and/or advanced metering infrastructure) by water suppliers by 2030, and the subsequent action by customers to address the leaks identified.

Further, we have examined the cost for implementing a revised indoor standard. The total anticipated cost range for reasonably complying with a 2030 standard in which all providers achieve a residential indoor per capita volume of 42 GPCD by 2030 is likely between $2.8 and $4.6 billion. See the attachment for further information on how we calculated this.

Thus, we request that the Study be submitted to the Legislature without a recommendation for a reduced indoor residential standard at this time. We believe that a more complete analysis of the cost and benefits of a reduced standard is needed, along with more study of other factors causing higher indoor use in some areas. Also needed to be examined carefully are the necessary stakeholder contributions regarding technical and local cost-effectiveness and rate affordability. After this work is done, a recommendation to reduce the indoor standard -- along with needed funding assistance for implementation -- may well be justified.

Thank you for the opportunity to comment. This is an important and potentially costly decision for the State of California if not done carefully. CalWEP looks forward to partnering with the State to ensure that we establish data-driven standards that maximize urban water use efficiency in a manner that also takes into consideration cost for local suppliers and ultimately ratepayers.

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