Bob Knox works at the Sagecrest Care center.
He says water that runs off the roof keeps two acres of landscaping green.
"We water everything: landscape, plants, grass, everything with the water. And if we can keep it from running down the street and reuse it on our landscape, why not?"
Three inches of rain will fill the center's 16,000 gallon rubber-lined tank.
There it's stored until needed.
The whole thing cost about $6,000.
A smaller system for homes would start at about $1,000.
"It's a little bit larger than you would have at your home, but we have about two acres here that we irrigate."
The system captures more than 1,000 gallons annually.
That's one month of free water each year, but remember, this is in sunny and dry Texas.
Your savings could be even bigger if you live in a wetter part of the country.