Hach-Darrow and her late husband, Clifford, founded the Hach Chemical Company in 1947 as a small water analysis company, which they grew into a multi-million-dollar chemical corporation. Hach-Darrow, who was an avid pilot, and her husband would fly a small plane around the US visiting customers and attending trade shows. The pair raised three children, Bruce, Mary, and Paul, each actively involved in the family business. The Hach family started the Hach Scientific Foundation in 1982 to promote chemistry education through scholarships. In 1995, Hach-Darrow married retired pilot Donald Darrow, changing her name from Kitty Hach to Kitty Hach-Darrow. In 1999, Hach-Darrow and her son, Bruce, sold the Hach Chemical Company to science and technology company Danaher.