Do automatic-flush toilets waste or save water?

Q: Most times when I use an automatic-flush toilet in a commercial building, it flushes two to three times. Do automatic-flush toilets waste or save water? – Ed Zajac, Orangevale

A: Your experience is common and it seems these devices do not save water, according to several studies, and may actually use significantly more than old-school manual valves.

John Koeller, a Yorba Linda-based engineer and water efficiency expert, said the primary benefit of automatic- or sensor-flush plumbing fixtures is improved hygiene, not water savings. Koeller is a partner in an organization called MaP Testing, which for years has conducted independent testing of various plumbing fixtures.

In 2010, Koeller and a colleague studied sensor-flush toilets in the real setting of a Florida office building. After months of monitoring, they found that sensor-flush toilets actually increased water consumption by 45 percent compared to manual-flush toilets. The cause was so-called “phantom flushing,” or multiple false flushes produced by over-active motion sensors on the toilets… Read More