United reacted to their 4-2 defeat at Accrington with a bright start and took the lead in the 15th minute when Scott Rendell headed keeper Michael Poke’s clearance into the path of strike partner Chris Zebroski, who volleyed home.
Gulls boss Paul Buckle had recalled experienced winger Wayne Carlisle – and was rewarded when the Irishman swooped from the right for Torquay’s second goal on 31 minutes.
They all but sealed the result in first-half stoppage time when Rendell headed in Jake Thomson’s corner for his fifth goal of the season.
United further increased their lead in the 68th minute when Carlisle’s hooked shot bounced off the bar and Zebroski headed home the rebound for his fourth goal in four games.
Substitute Elliot Benyon made it 5-0 in the 75th minute when he latched on to Thomson’s cross from the right and volleyed home from 15 yards.
The loss was Darlington’s fifth League Two defeat in a row.