Willows have an incredible root system. In a suburban setting they will find your sewer line and plug it. Unless like me you are in an odd and rare geological setting. My house at 50 meters above sea level is just 2 meters above an Ice Age marine beach. It is a water filled sedimentary layer with several natural springs along the street. I have taken advantage to plant an Arroyo Willow, Salix lasiolepis. It tapped the spring, and not the sewer. The tree is fine, but the added fun are Morning Cloak butterfly caterpillars.