Somewhere inside a bathroom at Fillmore Gardens, a senior housing community in Phoenix, a toilet had been quietly running for weeks. No puddle, no drip, nothing to tip anyone off. Just hundreds of gallons disappearing every day, hidden behind a single shared water meter that made the leak invisible on paper. 

This is a problem that plays out across the country. Now, a simple sensor is helping fix it. 

WHERE IT STARTED 

In 2021, the Pacific Institute, in our search to find innovative water resilience strategies, partnered with Sensor Industries to test a simple idea: put a small sensor on every toilet and let the data find what people couldn’t see. 

The first test came at MacArthur Park Tower in Los Angeles. That pilot site saved nearly a million gallons of water in its first year just by catching over 20 leaks that would have otherwise run for months unnoticed. 

A larger pilot soon followed in Los Angeles with 1,200 sensors across eight affordable housing properties managed by the Housing Authority of the City of Los Angeles (HACLA). Sensors there found that more than half of all toilet water use was being lost to leaks, not flushes. Fixing them cut water use by 11 percent and bills by 12 percent, work later honored with a 2025 One Water Award from the Metropolitan Water District of Southern California. 

“Millions of gallons of water run through our properties, so it’s important to us that we do our part to preserve and sustain wherever we can.” 

Tina Booth, Director of Asset Management, HACLA 

By 2026, the model has grown to 16 properties across California and Arizona, saving more than 14 million gallons of water every year. 

WHAT IS HAPPENING NOW 

This spring, that same model returned to Phoenix on a bigger scale. The City of Phoenix, the Pacific Institute, Sensor Industries, and Target expanded smart leak detection to all 120 units at Fillmore Gardens. 

Mayor Kate Gallego and Vice Mayor Kesha Hodge Washington along with the Sensor Industries crew joined residents and maintenance staff for the launch. Small leaks can lead to significant water loss over time and catching them early is what makes the difference. That urgency is real in Phoenix, a city bracing for cuts to its Colorado River supply in the years ahead. 

“We’re leveraging smart technology to fix leaks, reduce costs and protect our most precious resource. Every drop matters in the desert, and we’re proud to have private sector partners who understand the importance of investing in conservation.” 

– Phoenix Mayor Kate Gallego 

For residents, many of whom live on tight budgets, a hidden leak isn’t just wasted water. It means more money stays with the work of keeping housing affordable for them. Catching it early keeps savings where they belong and residents feel that stake themselves. In a survey across participating properties, over 90 percent said they feel a responsibility to help conserve water, and 85 percent said knowing their building is taking action makes them proud to live there. 

WHERE IT’S HEADED 

Fillmore Gardens is the latest example of a model that has continued to grow since its first pilot in Los Angeles. Beyond the water savings, the initiative has shown the value of the coalition behind it. It brings together people who don’t typically share a table including environmental researchers, affordable housing operators, water utilities, a technology partner, corporate funders, and local governments to solve a shared challenge. Convened by the Pacific Institute in partnership with Sensor Industries and the Bonneville Environmental Foundation, the initiative has created a replicable model for cross-sector collaboration that can scale to cities across the United States and beyond. 

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