Down the Drain: Why Cities Should Use Rainwater to Flush Toilets


Offset Potable Water Use &
Reduce Rainwater Runoff

Research by a team of Drexel University environmental engineers indicates that it rains enough in Philadelphia, New York, Seattle and Chicago that if homeowners had a way to collect and store the rain falling on their roofs, they could flush their toilets often without having to use a drop of municipal water.

Franco-Montalto_Drexel U“The study looks at four of the largest metropolitan areas in the country to see if it rains enough to make implementation feasible and, if everyone did it, what effect it would have on domestic water demand and stormwater runoff generation in those cities,” said Dr. Franco Montalto, an associate professor in Drexel’s College of Engineering, and director of its Sustainable Water Resource Engineering Lab, who led the research effort.

His research focuses on the development of ecologically, economically and socially sensible solutions to urban environmental problems with a focus on sustainable water resource engineering.

Key Finding

The study is one of the first to crunch the numbers and sort out just how feasible, and beneficial, it would be as a way of offsetting potable water use for non-potable purposes while at the same time reducing generation of undesirable urban stormwater runoff.

The team calculated that, with enough water storage capacity — a little more than a standard 1,000-US gallon home storage tank — a three person family in a home with the city’s average roof size would have enough water to cover over 80 percent of its flushes throughout the year simply by diverting their downspouts to collect stormwater.

To Learn More:

To download and read the complete article released by Drexel University, click on Down the Drain: Here’s Why We Should Use Rainwater to Flush Toilets