Born August 9, 1930, to Thomas Sr. and Thomasine Elizabeth Danforth Hagler of Augusta and grandson of John Carroll Hagler and Katherine Waterman, Thomas Waterman Hagler Jr. was educated in Augusta, graduating from Richmond Academy in 1948. He then earned a degree in mechanical engineering from Georgia Institute of Technology in 1952. Having been in ROTC, he entered the U.S. Air Force as a Second Lieutenant after graduation. Trained as a pilot, he was assigned to the 15th Tactical Reconnaissance Squadron in Japan in 1954. Upon completing his time in the service, Tom and his wife, Billie, came to Augusta.

 Hagler’s father and uncles were prominent businessmen in the brick and tile industry in Augusta. In 1948, Tom’s father and uncle purchased Georgia Ironworks. Upon his return to Augusta, he went to work for the company as an engineer in 1955. Tom was Chief Engineer when his brother Danforth W. Hagler developed the first hydraulic slide rule used to perform calculations for slurry (liquids with solids in suspension) pumps and pipelines; Thomas Hagler wrote the user manual, explaining not only how to use it, but the theory behind the hydraulic problems. Prior to this invention, complicated and time-consuming calculations had to be made using a manual over 100 pages long. The GIW Hydraulic Slide Rule is now in the Smithsonian Institute in Washington DC.

In 1963, Tom Jr. became Vice President and Chief Engineer and, in 1971, President and Chief Executive Officer of GIW. When his brother-in-law John Lee became president in 1986, he continued to serve as CEO. In 1987, John Lee and Hagler completed a leveraged buy-out with cousin, John C. Hagler III, along with brother Danforth (Danny) Hagler. Thomas became chairman of the Board and CEO of the company until 1996, while Lee became President and Chief Operating Officer. In 1988, GIW became part of KSB AG of Frankenthaler, Germany, the second largest pump company in the world. Tom Hagler Jr. became its Slurry Pump Division Manager.

He was a member of the Georgia Tech Academy of Distinguished Engineering Alumni. In the mid-1990s, he served on the institution’s Mechanical Engineering Department Advisory Board. In 1985, he served on the CSRA Advisory Board that brought the National Science Center to Augusta. In retirement, he published several books of a religious nature. His four sons all graduated from Georgia Tech.