Drain water heat recovery (DWHR) is a technology used to conserve energy for water heating. The technology utilizes a heat exchanger to transfer heat from warm drain water to cold supply water. Drain water heat exchangers can recover heat from a variety of sources, including showers, bathtubs, sinks, dishwashers, clothes washers, and industrial processes.
DWHR technology has been available since 1986, and was introduced into Title 24, Part 6 for residential applications for the 2019 code cycle (Statewide CASE Team n.d.). In the 2019 Title 24, Part 6 requirements, DWHR is part of an alternative prescriptive pathway for single family and low-rise multifamily buildings. The alternative prescriptive pathway allows gas storage water heaters and heat pump water heaters to be installed in combination with other efficiency measures including DWHR (Section 150.1(c)8A). HERS-verified DWHR is also one option for achieving CALGreen Tier 2. DWHR is currently available as a compliance option for all residential buildings and for High-Rise Residential Living Spaces within nonresidential buildings. Prior to adopting DWHR requirements for 2019 Title 24, Part 6, energy savings from shower DWHR in North America were demonstrated in the Provinces of Ontario and Manitoba, Canada, where shower DWHR is a requirement for prescriptive compliance with the residential energy code.
A separate, concurrent 2022 code change proposal by the Statewide CASE Team attempted to make shower DWHR a primary prescriptive requirement for all multifamily buildings. The multifamily DWHR measure was found to be not cost effective due to the submetering requirements included in Senate Bill 7 (SB 7, Wolk 2016), which requires independent submetering of all domestic water entering residential dwelling units. The submetering requirements of SB 7 apply to residential buildings only and would not affect DWHR installed in nonresidential buildings.
- Final CASE Report Now Available – Nonresidential Drain Water Heat Recovery
- Draft CASE Report – Nonresidential Drain Water Heat Recovery
- Presentation – Oct 3 – Multifamily and Nonresidential Water Heating Utility-Sponsored Stakeholder Meeting
- Notes – Oct 3 – Multifamily and Nonresidential Water Heating Utility-Sponsored Stakeholder Meeting
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The Statewide CASE Team values input from all stakeholders engaged in the Title 24, Part 6 code change process. We encourage the open exchange of code change comments and concerns.
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