Mercy Housing was an early adopter of central heat pump water heater systems for multifamily and being a leader in new electrification technology does not come without challenges. When the heat pump water heating project began at Presentation Senior in San Francisco, no one was aware that the outdated plumbing infrastructure system would reject the new technology and create crossover and distribution imbalance issues. It is standard practice at Mercy Housing to check for potential crossover and distribution imbalance issues before engaging in a central heat pump retrofit project. From the lessons learned at Presentation Senior Community and our new standard practices, multiple heat pump retrofits have been implemented at Mercy Housing communities with no such problems.

Solving the hot water distribution issues at Presentation Senior Community has been a journey. Several solutions have been proposed and implemented with varying degrees of success, but achieving consistent hot water availability for all apartment homes was challenging. Sally Chiu (the Property Manager at Presentation) and Paul Tonga (the areas Regional Facilities Director) both started working on this problem in early 2024. Since they began devoting their time to the hot water issues at Presentation, we have seen the greatest level of success to date. The hot water at the property is currently the best it has been since 2017.

Sally Chiu

Sally has played a critical role in the efforts to regain consistent hot water at Presentation Senior Community. She helped set up a working group that meets every week to discuss the problems at the property. She arrives every week prepared to present the latest information from residents. She keeps residents informed of the efforts. She asks residents about hot water who otherwise would not come forward to report on the issues. Sally has also worked to coordinate site visits from multiple groups that have investigated these issues. Her help on this project has been instrumental in improving the access to hot water that residents now receive.

Paul Tonga
Paul has also been working on this project for almost two years and has taken direct control over the maintenance and investigative side. He has been a part of the weekly meetings and has provided the group with deep technical knowledge related to problems at this senior community. He has also worked with multiple partners to try to identify the source of the issues. Paul visited the community several times and helped to install many of the solutions that improved access to hot water. Some of the solutions installed include circuit setters, thermostatic balancing valves, and faucet cartridges.

Special Thanks
We would also like to include a special thanks to everyone who attends our weekly meeting or who has stepped in to help with this project:

• Matteo Milesi
• Larisa Abramova
• Vicky Zeng

Thank you all for your leadership, dedication, and commitment to sustainability.