Living in Germany until 1949, their application to immigrate to the United States was refused on account of the large size of the family.

After spending four weeks in hospital due to a case of polio, Konrads swam therapeutically to rebuild strength.

[5] This led to Konrads being selected for the team to attend the 1956 Summer Olympics in Melbourne, although as a reserve he did not compete in any form.

[4] Every day, John and his younger sister Ilsa cycled to the Bankstown pool before sunrise, for a two-hour training session, before returning home for breakfast and then attending school.

[9][10] At the Olympics in Rome, fellow Australian and defending 400 m and 1500 m champion Murray Rose had returned from the United States to compete, and qualified fastest for the 400 m final, although well outside Konrads' mark.

Although George Breen of the United States had attacked early, Konrads stuck to his raceplan and overhauled him to win in an Olympic record time of 17 m 19.6 s, with Rose second.

[2][11][12] In the 4 × 200 m freestyle relay, Konrads combined with Devitt, Rose and David Dickson to claim a bronze medal behind the United States and Japan.

[13] After the games, Konrads accepted a swimming scholarship at the University of Southern California, where his performances decreased over time.

After retirement, Konrads became a swimming coach, and with his marketing degree from USC,[14] he eventually rose to the Australasian directorship of L'Oréal.