The victory came with a successful defence of the 100m individual medley in a time of 57.37. The Edinburgh 21-year-old was also the defending champion in the 200m backstroke but had to settle for second best behind Warrender clubmate Craig McNally. Edinburgh University's Callum Shaw took bronze.
Smith took bronze in the 400m freestyle.
In the 800m freestyle, Warrender's Helen McRoberts claimed the silver medal behind multi-winner Hannah Miley with a time of 8:53.78.
Warrender youngster Fiona Donnelly made it a day to remember when she won the 50m breaststroke and set a new Scottish junior record of 28.92.
In the men's 50m breaststroke, Warrender's Craig Benson finished seventh in 29.45 – and that was good enough to claim a new Scottish junior record and the national junior title.
But the stand-out performer was Garioch's Miley, who collected golds in the 800m, the 100m breaststroke (1:10.24) and the 200m individual medley (2:13.76) before rounding things off with a fine 2:12.99 in the 200m butterfly.