Model-eliciting activities (MEAs) create opportunities to incorporate new standards and evaluate teacher performance. MEAs are simulated real-world problems that integrate engineering, mathematical, and scientific thinking as students find solutions for specific scenarios. In this chapter, an MEA was created that would challenge students to build a cost-effective water filter to clean a water sample of pollutants. Using MEAs affords students the opportunity to explore a new way of problem solving that requires them to plan, build, test, and redesign. A materials list, teacher background information, assessments, and outcomes are provided. This book selection includes the Table of Contents, Introduction, References, and Index.